Conodont Apparatus Reconstruction from the Lower Carboniferous Hart River Formation, Norther Yukon Territory

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2016 Conodont Apparatus Reconstruction from the Lower Carboniferous Hart River Formation, Norther Yukon Territory

Lanik, Amanda

Lanik, A. (2016). Conodont Apparatus Reconstruction from the Lower Carboniferous Hart River Formation, Norther Yukon Territory (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/25420 http://hdl.handle.net/11023/3324 master thesis

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Conodont Apparatus Reconstruction from the Lower Carboniferous Hart River Formation,

Northern Yukon Territory

Amanda Lanik

A THESIS

SUBMITTED TO THE FACULTY OF GRADUATE STUDIES

IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE

DEGREE OF MASTER OF SCIENCE

GRADUATE PROGRAM IN GEOLOGY AND GEOPHYSICS

CALGARY, ALBERTA

SEPTEMBER, 2016

Conodonts sampled from the Lower Carboniferous Hart River Formation have yielded abundant, well-preserved elements with a relatively low diversity of species. In addition, they do not display much platform-overrepresentation, a phenomenon affecting the majority of Late

Paleozoic conodont samples. These qualities make the Hart River conodont samples ideal for statistical apparatus reconstruction. The elements were divided into groups based on morphology and counted. Cluster analysis, in addition to empirical observations made during the counting process, was then used to reconstruct the original apparatus composition for the species present. Five partial to complete apparatus reconstructions were made, belonging to the species Bispathodus sp. A, Bispathodus stabilis, Gnathodus homopunctatus, Gnathodus texanus, and Vogelgnathus gladiolus. The co-occurrence of these species indicate an early Visean age for the Hart River Formation. This differs slightly from the late Visean to early Serpukhovian age previously suggested for the Hart River Formation. The apparatus reconstructions prompted the reassignment of what has been called Lochriea homopunctatus in previous studies to the genus

Gnathodus, and the new identification of Bispathodus sp. A, formerly interpreted as

Rachistognathus prolixus. The apparatus reconstructions made in this study show new morphology for taxa that are both stratigraphically and evolutionarily important, indicating greater taxonomic complexity than was previously identified.

ii Acknowledgements

I would like to acknowledge the assistance of Mickey Horvath, for the preparation of thin sections, Michael Schoel, for help imaging the elements using the Scanning Electron

Microscope, and Richard Fontaine, for access to the Hart River samples at the Geological Survey of Canada. I would also like to thank Chad Morgan, Amanda Godbold, Shane Schoepfer and

Elinda Dehari, for discussing ideas, editing writing, and moral support throughout this project.

Finally, I would like to acknowledge my advisor Charles Henderson, not only for his exceptional guidance, but for introducing me to aspects of conodont research that have sparked my curiosity.

iii Table of Contents

Abstract ...... ii Acknowledgements ...... iii Table of Contents ...... iv List of Tables ...... v List of Figures ...... vi

CHAPTER ONE: INTRODUCTION ...... 1 1.1 Purpose and overview of study ...... 1 1.2 Introduction ...... 3 1.2.1 Conodont Studies: A Brief History ...... 3 1.2.2 Conodont Taphonomy ...... 8 1.2.3 Previous Work ...... 12 1.3 Expanded methods ...... 13 1.3.1 Creating morphologic groups ...... 13 1.3.2 Counting and Empirical Observations ...... 14 1.3.3 Thin Section Preparation ...... 14 1.3.4 Rarefaction ...... 14 1.3.5 Cluster Analysis ...... 15 1.4 Expanded Results ...... 17 1.4.1 Morphologic groups ...... 17 1.4.2 Element abundance and distribution ...... 27 1.4.3 Thin Sections ...... 28 1.4.4 Empirical Observations ...... 31 1.4.5 Rarefaction ...... 42 1.4.6 Cluster Analysis ...... 42 1.4.7 Biostratigraphy and Paleoenvironment ...... 45 1.5 Discussion ...... 49 1.5.1 Combined Cluster Analysis Results: ...... 51 1.6 Role of the student ...... 52

CHAPTER TWO: CONODONT APPARATUS RECONSTRUCTION ...... 54 2.1 Introduction ...... 54 2.1.1 Study area.— ...... 59 2.2 Materials and methods ...... 62 2.3 Results ...... 65 2.4 Discussion ...... 66 2.5 Systematic paleontology ...... 69 2.6 Conclusions ...... 93

CHAPTER THREE: MAJOR CONTRIBUTIONS AND FUTURE WORK ...... 96 3.1 Major Contributions ...... 96 3.2 Future Work ...... 97

iv List of Tables

Table 1.1: Element type and abundance………………………………………………27 Table 1.2: Thin section descriptions………………………………….……………… 28 Table 2.1: Species and abundance…………………………………………………….62

v List of Figures

Figure 1.1: Generalized Ozarkodinid apparatus……………………………………….….9 Figure 1.2: P1 descriptive terminology……………………………………………….… 18 Figure 1.3: P1 descriptive terminology……………………………………………….….19 Figure 1.4: P2 descriptive terminology…………………………………………………..19 Figure 1.5: M descriptive terminology……………………………………………….….20 Figure 1.6: S0 descriptive terminology…………………………………………………..20 Figure 1.7: S descriptive terminology……………………………………………….…..21 Figure 1.8: P1 element types………………………………………………………….….22 Figure 1.9: P2 element types……………………………………………………………..23 Figure 1.10: M element types…………………………………………………………....23 Figure 1.11: S0 element types…………………………………………………………....24 Figure 1.12: S element types…………………………………………………………….25 Figure 1.13: Element types with distribution one ……………………………………....30 Figure 1.14: All elements with distribution one highlighted……………………...…….32 Figure 1.15: Element types with distribution two ………………………………...…….33 Figure 1.16: All elements with distribution two highlighted………………………...….35 Figure 1.17: Element types with distribution three ………………………………….….36 Figure 1.18: All elements with distribution three highlighted………………………….. 38 Figure 1.19: Element types with distribution four …………………………………..…. 39 Figure 1.20: All elements with distribution four highlighted………………………...….40 Figure 1.21: Cluster analysis results, Jaccard similarity…………………………………41 Figure 1.22: Cluster analysis results, Bray-Curtis similarity………………………...…..43 Figure 1.23: Species ranges and Hart River Formation Age..…………………...………45 Figure 2.1: Map of study area……………………………………………………...…….61 Figure 2.2: Cluster analysis results, Bray-Curtis similarity…………………….....……..65 Figure 2.3: Bispathodid elements…………………………………………………...……80 Figure 2.4: Gnathodus homopunctatus elements……………………………………...... 90 Figure 2.5: Gnathodus texanus and Vogelgnathus gladiolus elements……………...…...93

List of Plates

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Chapter One: Introduction

1.1 Purpose and overview of study

Conodonts are microscopic, tooth-like fossils that can be found in Cambrian to Triassic marine strata worldwide. Conodonts have been used extensively as biostratigraphic tools, defining many of the divisions in the Paleozoic and early Mesozoic portions of the Geological

Time Scale (Gradstein et al., 2012). In addition, conodonts are used to determine thermal maturation of rocks and paleotemperatures by using the Conodont Alteration Index (CAI) and oxygen isotopes respectively (Epstien et al., 1977; Joachimski et al., 2009). Despite this wide usage of conodonts to address geologic questions since the 1930’s, the conodont-bearing animal has been identified more recently (Briggs et al., 1983). There are also major aspects of conodont biology that are either poorly understood or entirely unknown. The goal of this project is to contribute to the understanding of one of these unresolved aspects – the conodont apparatus.

Conodonts, like many animals, had a variety of morphologically diverse elements that worked together to process food (Goudemand, et al., 2011). The combination of all elements that a single conodont animal possessed is called an apparatus. Apparatuses are often recognized via natural assemblages. A natural assemblage can manifest either as clusters of elements found on bedding planes or clusters of elements that have been chemically fused together (Sweet,

1988). However, the preservation of original apparatuses is relatively rare and not evenly distributed spatially or temporally. This dearth of direct evidence makes it difficult to understand which elements belonged to the same species, often causing taxonomic redundancy.

To reconstruct apparatuses, in cases where more direct methods are unavailable, conodont researchers have conducted statistical analyses on disjunct conodont elements extracted either by dissolving or disaggregating host rock (Kohut, 1969; Horowitz and Rexroad, 1982). These

statistical methods can greatly increase the number of multi-element conodont species recognized, providing data to integrate with apparatuses known from direct observation.

Samples collected from the Lower Carboniferous Hart River Formation have yielded abundant, well-preserved conodont elements. These samples have relatively low diversity and the elements occur in close to biologically correct proportions (Purnell and Donoghue, 1997), making them ideal for statistical apparatus reconstruction. The abundance of non-platform elements (ramiform and blade pectiniform elements) recovered is unusual, especially for samples from the Late Paleozoic. Thin sections have been made for select samples to assess any correlation between lithology and element abundance.

The elements have been divided into groups based on morphology and counted. To reconstruct the original apparatus composition of the species present, cluster analysis was run using the previously identified element groups, taking into account distribution and abundance.

These reconstructions also incorporate empirical observations that were made during the counting process. The reconstructed apparatuses are compared to previously proposed apparatuses, highlighting similarities and differences. The differences observed could be due to geographic variation, evolution in long-lived taxa, or convergence of the P1 elements upon which most species identifications rely.

Apparatus reconstruction projects, such as the one presented here, are vital in establishing a robust multi-element taxonomy for conodonts. Traditional conodont taxonomy is limited because it is based on the morphology of platform elements only, which make up 2 out of the 15 elements in the apparatus. While there have been more apparatuses discovered recently (Atakul-

Ozdemir et al., 2012; Goudemand, et al., 2012; Slavik, 2011; Tolmacheva and Purnell, 2002), the development of new apparatus reconstructions should be sought whenever possible. This is

especially true because some apparatuses that have been reconstructed, including those presented in this study, do not match up with previously reconstructed apparatuses of the same species or genus. This suggests that more work needs to be done to understand if these morphologic variations are real or if the reconstructions themselves are flawed. Furthermore, these reconstructions have increasingly been used to research other aspects of conodont biology, such as the relationships between conodont groups (Atakul-Ozdemir et al., 2012; Donoghue et al.,

2008). The establishment of robust, consistent apparatus reconstructions is essential for any of these types of studies and can only be accomplished by utilizing samples, such the ones from the

Hart River Formation, that are ideally suited for statistical apparatus reconstruction.

1.2 Introduction

1.2.1 Conodont Studies: A Brief History

In 1856 Heinz Christian Pander described the first conodonts, interpreting them as teeth or jaw components belonging to an unidentified extinct group of fish (Sweet and Donoghue,

2001). This interpretation is reflected in the name used by Pander, Conodonten, meaning cone- shaped teeth (Pander, 1856). However, subsequent researchers did not universally accept

Pander’s initial interpretation that conodonts were teeth or jaw components. Conodonts have been interpreted as a variety of different structures, including internal support structures, spines, copulative claspers, or a feeding apparatus (Hass, 1962). In addition to uncertainty over the function of conodonts, there was considerable debate among early researchers over the classification of conodonts. Conodonts have been placed in groups as diverse as worms, mollusks, fish, and even vascular plants (Hass, 1962). Recent studies (Briggs et al., 1983;

Purnell, 1995; Donoghue et al., 2000; Donoghue and Purnell, 1999b) have shed light on these traditionally enigmatic aspects of conodont biology, however a lot of early research was

established without a true knowledge of what the conodont animal looked like or the function that the elements performed.

In the early 1930’s, conodonts began to be widely used for biostratigraphic purposes

(Branson and Mehl, 1933; Branson and Mehl, 1934). Conodonts are easy to collect, evolved rapidly, and often have a global distribution, making them ideal index fossils. Edwin Branson and Maurice Mehl, of the University of Missouri, were some of the first paleontologists to recognize the stratigraphic potential of conodonts and implement research to fulfill this potential.

Starting with their publication of Conodont Studies in 1933 and 1934, Branson and Mehl became pioneers in the field, not only contributing immensely to an understanding of conodont distribution in North America, but also establishing much of early conodont taxonomy (Sweet,

1988). Their work encouraged others to take up the study of conodonts, and due to this, their views on conodont biology shaped much of the research that was subsequently conducted.

Among other aspects, this includes their views on how conodont species should be defined.

When Pander first described conodonts, he based species on the morphology of individual elements (Sweet, 1988). This species concept assumes that all the elements belonging to a species conform to a single morphology. Branson and Mehl followed this practice, establishing this as the standard among early conodont researchers (Branson and Mehl, 1933;

Branson and Mehl, 1934). However, it was proposed by some that conodonts instead possessed elements with a variety of different morphologies. The first to propose this idea was Hinde in

1879. Hinde (1879) discovered a specimen from the Genesee shale of New York that displayed

“a group of various forms of teeth and plates that have been compressed together in such a manner as to show that they must have belonged to the same animal”. Hinde was describing what has subsequently become known as a natural assemblage: a conodont specimen that has all

its elements preserved together, often found on bedding planes or in fused clusters. While this group of elements would be later interpreted to be a coprolitic cluster rather than a true natural assemblage, this was the first time the description of a conodont species (Polygnathus dubius) included multiple morphologically distinct elements.

Around the time Branson and Mehl were publishing their first papers on conodont taxonomy, both Hermann Schmidt (1934) and Harold Scott (1934) discovered numerous

Carboniferous-aged natural assemblages. Scott was definitive about the conclusions drawn from these specimens, asserting, “the conodont assemblages herein described definitely prove that teeth of various kinds, representing more than one genus in our present scheme of classification, existed in the mouth of one individual” (1934). Branson and Mehl rejected this conclusion, claiming the assemblages were instead fecal pellets from predators of conodonts (according to

Sweet and Donoghue, 2001).

By rejecting this concept, Branson and Mehl were reaffirming the taxonomic procedure they had developed (based on single element morphology; Sweet and Donoghue, 2001). The tendency to describe new conodont species based only on the morphology of a single element persisted. Due to this practice, the majority of conodont species recognized today rely exclusively on the morphology of one element, with the other elements of the apparatus being poorly resolved or unknown. This prevalence of form-taxonomy is in part due to the rarity of preserved natural assemblages. However, in the 1960s, a new methodology was developed that would allow for the recognition of multi-element species, even in cases were the original apparatus was not preserved (Kohut, 1969). While direct observation of an apparatus is preferable due to the lack of ambiguity regarding element association and the demonstration of

relative size and orientation of elements, apparatus reconstruction from disjunct elements greatly increases the number of multi-element conodont species recognized.

By the 1960s, the practice of dissolving carbonate rocks with acid to extract elements had become standard among conodont workers (Sweet and Donoghue, 2001). This led to the accumulation of vast collections of elements that, while disarticulated, have known distributions and associations. Conodont workers started noticing that certain elements typically occur together, suggesting that these elements are related to each other in some way. This relationship could be due to taphonomic processes such as sorting. It could also be due to the co-occurring elements coming from species that consistently lived in the same environment. Finally, associations could be caused by the elements physically belonging to the same species. Some researchers started to develop more quantitative methods, such as cluster analysis, to pick out these reoccurring groups in hopes of recognizing original apparatus composition (Kohut, 1969).

With the development of this new technique, in addition to the discovery of more natural assemblages, multi-element taxonomy has developed greatly since the 1960s.

In addition to their biostratigraphic value, in the 1970s, USGS paleontologist Anita Harris discovered another useful characteristic of conodonts (Epstein et al., 1977). Harris found that as conodonts are heated they change colour, going from light amber, to black, to clear with increasing temperature (Epstein et al., 1977). This phenomenon is known as the Conodont

Alteration Index (CAI) and certain CAI values correspond to the potential presence of oil or natural gas (Belka, 1993). The colour change is due to alteration of the organic material found within the otherwise largely phosphatic elements, and since this corresponds to the maximum temperature to which the conodonts have been subjected to, the thermal maturity of the surrounding sediments can be determined (Epstein et al., 1977). This method is fast, easy, and

cheap when compared to other methods of assessing organic metamorphism, making this use of conodonts popular in the oil and gas industry (Harris, 1981).

In 1983, Briggs, Clarkson, and Aldridge made perhaps the biggest discovery in conodont research since Pander’s original description over a century earlier – the first preserved conodont- bearing animal. The discovery was of a soft bodied, 40.5 mm long and 1.8 mm wide eel-like organism that contained a natural assemblage of conodont elements in the head region (Briggs et al., 1983). While the situation of the elements did not prove their function beyond dispute, the authors thought the interpretation of conodonts as teeth seemed probable in light of their new discovery. After this discovery, most authors agreed that conodont elements were used to ingest food, however, whether these elements were used for active mastication or passive filter feeding is still debated (Purnell, 1994; Turner et al., 2010). Wear patterns, which are interpreted as being formed via element occlusion, have been recognized on element surfaces and support the more active role of elements during feeding (Donoghue and Purnell, 1999).

Conodonts have been used extensively to provide temporal constraint for Paleozoic and

Triassic strata (Gradstein et al., 2012). In addition, they have been widely used to determine thermal maturity, facilitating oil and natural gas exploration. Despite this wide usage, there has been a lot of contention over the biological aspects of conodonts, specifically the affinity of the conodont animal (Scott, 1934; Turner et al., 2010; Donoghue et al., 2000) the function of conodont elements (Turner et al., 2010; Purnell and Jones, 2012; Jeppsson, 1979), and the presence of a morphologically diverse apparatus (Hinde, 1879; Bryant, 1921; Scott, 1934;

Rhodes, 1952; Sweet, 1988). In his 1934 publication, Scott discussed this peculiar quality of conodonts, commenting, “Probably no group of fossils has been as much studied and as little understood”. This was certainly true in the early days of conodont research, however recent

research has illuminated some of these enigmatic aspects of conodont biology. The discovery of the first conodont animal resolved a lot of the more contentious aspects, however there is still some debate over the question of conodonts being vertebrates (Donoghue et al., 2000; Turner et al., 2010), and the function of elements as teeth (Turner et al., 2010; Purnell and Jones, 2012).

Additionally, while researchers have generally accepted the advantage of multi-element taxonomy, there is a lot of work that needs to be done to expand current multi-element taxonomy, especially since these reconstructions are being used to understand conodont evolution and relationships.

1.2.2 Conodont Taphonomy

Like any fossil group with multiple parts, conodonts are found in varying degrees of preservation, ranging from totally disarticulated to soft tissue and mineralized elements preserved in their original orientation. When compared to the abundance of disarticulated conodont elements found in the rock record, the occurrences of elements preserved in their original orientation are relatively rare. This could be due to the way conodonts are often collected and processed – by dissolving or disaggregating the host rock and picking through the residue to recover elements. This process will disarticulate any elements in their original orientation, making it impossible to directly observe any natural assemblages that may have been present. However, this processing technique should not affect the proportions of different elements recovered from rock samples.

Conodonts have been split into seven orders, with the majority of bedding plane assemblages and apparatus reconstructions belonging to the Order Ozarkodinida (Purnell and

Donoghue, 1997). Based on bedding plane assemblages, it has been determined that ozarkodinid conodonts possessed an apparatus that contains 15 elements, with all but one element occurring

as dextral and sinistral pairs (Aldridge, 1995; Figure .1). The ozarkodinid apparatus contains four pectiniform elements, two of which typically display expanded platform morphology (P1) and two of which have a blade-like morphology (P2). The rest of the elements are ramiform or bar-shaped elements. The platform elements occur in the posterior-most position of the apparatus and only make up 2 out of 15 of the elements in the apparatus. However, these platform elements often are the vast majority of the elements recovered when sampling for conodonts. In disjunct sets of elements, this preponderance of platform elements becomes increasingly pronounced in younger strata, while natural assemblage element proportions remain static (Purnell and Donoghue, 2005). This phenomenon has been called platform- overrepresentation because the proportion of platform elements recovered is far greater than bedding plane assemblages would suggest is the correct biologic proportion.

Figure 1.1: Generalized Ozarkodinid apparatus with element notation (modified from

Aldridge et al., 1995).

Platform over-representation has been explained in various ways, with researchers attributing it to predation and digestion of conodonts, a preferential shedding of the other elements, a variation in the conodont apparatus during ontogeny (Merrill and Powell, 1980), or the hydraulic sorting of different element morphologies (Purnell and Donoghue, 2005; Helms and Over, 2006). Platform over-representation becomes increasingly prominent in younger samples, suggesting that, at least in part, it is controlled by evolutionary changes of the conodont apparatus (Purnell and Donoghue, 2005). Purnell and Donoghue (2005) suggested that as conodonts evolved, the relative size of the P1 elements changed, causing a change in the hydrodynamic behaviour of the P1 elements when compared to the rest of the apparatus. This could lead to sorting of the different conodont elements based on element size (Purnell and

Donoghue, 2005). It has been demonstrated by others authors that different elements will have different hydrodynamic behaviours depending on their size and morphology (McGoff, 1991;

Broadhead et al., 1990). However, it is important to note that the hydrodynamic behaviour of individual elements would not have much bearing on cases where the conodont did not decompose and disarticulate prior to burial. It has yet to be shown that the relative size of elements within an apparatus truly does become more disparate in younger taxa, nor have ramiform overrepresented or ramiform-only samples been found as frequently as would be expected if conodont elements were widely sorted.

Another proposed cause of platform over-representation involves the number of elements in a conodont apparatus changing through ontogeny. Merrill and Powell (1980) proposed that some conodont species developed their ramiform elements first, with platform elements developing later in ontogeny. They also proposed that as these platform elements grew and the conodont reached adulthood, the ramiform elements were subsequently resorbed, leaving an

adult conodont with a platform-only apparatus (Merrill and Powell, 1980). This theory would account for platform-overrepresentation by suggesting that the ramiforms are not missing at all, but instead were never associated with adult platform elements. However, other researchers have rejected this ontogenetic model (Purnell, 1994). Purnell (1994) examined the growth of different types of elements of two Carboniferous taxa, Idiognathodus sp. and Gnathodus bilineatus. He found that apparatuses that contained large, “adult”-sized platform elements also contained a full complement of ramiform elements. In addition, Purnell (1994) found that the growth of ramiform elements was continuous, while Merrill and Powell’s model would predict ramiform growth to stop or even reverse as conodonts reached adulthood and ramiform elements were resorbed.

While there have been many suggestions as to what causes platform-overrepresentation, no widely accepted hypothesis has emerged for this phenomenon. Regardless, this phenomenon is very important to consider when reconstructing apparatuses from sets of disjunct elements, and probably one of the major reasons this method of apparatus reconstruction has not been more widely employed. It is impossible to use the abundance and occurrence of different types of elements to tease out anatomical associations when well over half the elements are typically missing. The prevalence of platform-overrepresentation, especially in Late Paleozoic and

Mesozoic samples, makes it especially important to take advantage of those rare samples that do not display significant platform-overrepresentation to reconstruct original apparatus composition.

This is why samples from the Carboniferous Hart River Formation, which display minimal platform-overrepresentation, are herein used to create apparatus reconstructions.

1.2.3 Previous Work

For information about the Hart River Formation and previous biostratigraphy, refer to the

Study Area section of Chapter Two.

There are two ways to reconstruct conodont apparatuses – either by direct observation on bedding plane assemblages or fused clusters, or indirectly through statistical analysis. Many authors have used bedding plane assemblages and fused clusters to recognize apparatuses for different genera and species of conodonts (Purnell and Donoghue, 1998; Johnston and

Henderson, 2005; Varker, 1994; Scott, 1942; Norby and Rexroad, 1985). Some previously identified bedding plane assemblages/fused clusters that are relevant to this study include

Bispathodus aculeatus, Lochriea commutata, and Gnathodus bilineatus described by Purnell and

Donoghue (1998), Bispathodus stabilis described by Johnston and Henderson (2005), Gnathodus bilineatus, and Lochriea sp. described by Varker (1994), Lochriea montanaensis and Lochriea bigsnowyensis described by Scott (1942), and Vogelgnathus campbelli described by Norby and

Rexroad (1985). Specific aspects of these apparatuses will be discussed in the Systematic

Paleontology portion of Chapter Two, and the reconstructed apparatuses from the Hart River

Formation will be compared to previous findings.

While directly observing an apparatus in its original orientation is preferred, many authors have used disjunct elements to reconstruct apparatuses when natural assemblages are not available (Horowitz and Rexroad, 1982; Kohut, 1969; McHargue, 1982; Over, 1992; Purnell and von Bitter, 1992; Grayson et al., 1990). This method of reconstruction has been implemented in different ways, with some authors taking a more quantitative approach, using statistical methods that assess element co-occurrence (Horowitz and Rexroad, 1982; Kohut, 1969). Other authors choose to take a more qualitative approach by comparing relative abundances of elements,

stratigraphic ranges of those elements, and similarities in element morphology (McHargue,

1982). Some previously reconstructed apparatuses that are relevant to this study include

Bispathodus stabilis reconstructed by Over (1992), Vogelgnathus campbelli, Vogelgnathus postcampbelli, and Vogelgnathus gladiolus reconstructed by Purnell and von Bitter (1992), and

Gnathodus bilineatus, Idiognathoides sinuatus, Gnathodus sp. aff Gnathodus girtyi,

Neognathodus higginsi, and Neognathodus bassleri reconstructed by Grayson et al. (1990).

Specific aspects of these apparatuses will be discussed in the Systematic Paleontology portion of

Chapter Two, during which time the reconstructed apparatuses from the Hart River Formation will be compared to previous findings.

1.3 Expanded methods

1.3.1 Creating morphologic groups

Designating the different morphologically distinct groups of elements and assigning elements to these groups was the most important and time-consuming portion of this study. In addition, it was likely one of the more subjective processes and therefore required special attention and care. This is a key step because the groups created during this step affect all of the subsequent steps, including the quantitative analyses. In this section, I will discuss the thought process behind this work.

To create groups, the elements were viewed, noting new morphologically distinct elements as they were observed. Special attention was paid to ontogeny, to ensure that juvenile elements (the smallest elements in a growth series) were not placed in groups different from their adult counterparts. In addition, the groups were created from a population perspective, with slight morphologic variation within groups being acceptable, as long as that variation is continuous.

1.3.2 Counting and Empirical Observations

After the element types were established, the elements were counted to determine the abundance and distribution. To avoid counting multiple fragments of the same element, only elements still possessing more than half of the basal cavity were counted. While this measure was necessary to avoid inflating counts of the more fragmented elements, it should be noted that this process could favour elements with large, easily seen basal cavities (such as the P1 elements) and hinder the counting of elements with very small basal cavities (such as the S elements).

Empirical observations were made during the counting process concerning the abundance and distribution of the different element types. These empirical observations resulted in the first ideas about possible associations of the element types; those ideas were later compared with the associations produced by cluster analysis.

1.3.3 Thin Section Preparation

Thin sections were made of samples 1028-17, 1028-18, 1028-21, 1028-22, 1028-23,

1028-25, 1028-26, and 1028-27, resulting in eight thin sections overall. Preparations were made by cutting rock samples into 4 cm by 2 cm stubs using a rock saw. Mickey Horvath then prepared these stubs into thin sections at the University of Calgary.

1.3.4 Rarefaction

One method that was used to ensure the Hart River samples are representative of the original conodont population is rarefaction. Rarefaction is a technique that uses number of specimens sampled and the number of species found to assess the species richness of a sampled population (Hammer and Harper, 2008). This technique can determine if the true diversity has been captured by a sample, or if further sampling should be done. The element counts were entered into PAST 3.12 (Paleontological Statistic Software Package) and rarefaction was

performed using this program. Because a single conodont species has more than one distinctive element type, only the P1 element counts were entered to ensure the number of species recovered was not artificially increased.

1.3.5 Cluster Analysis

In addition to using empirical observations to reconstruct the apparatuses for these samples, a statistical approach was also employed. The combination of both qualitative and quantitative methodologies increases the credibility of the analysis performed, allowing the most robust apparatus reconstructions possible.

It was determined that significant post-depositional taphonomic bias is unlikely due to the minimal platform overrepresentation, the presence of a variety of element shapes and sizes, and the excellent preservation of the elements,. In addition, these samples display high abundances of conodont elements, but low diversity. This means that statistical methods can be used to assess the co-occurrence of the elements, which can be interpreted as representing the original apparatus composition. Cluster analysis was used to assess the co-occurrence of the disjunct elements. PAST 3.12 (Paleontological Statistical Software) was used to perform the cluster analysis. These associations will subsequently be compared with the associations produced via empirical observation, highlighting the strengths and limitations of both methods.

Cluster analysis is a method that uses a chosen similarity index to construct a hierarchical tree, with groups and subgroups corresponding to relatedness (Hammer and Harper, 2008). In this study the results of two similarity indices were examined, the Jaccard coefficient (�) and the

Bray-Curtis measure. The Jaccard coefficient is as follows:

� � = � + � + �

� is the Jaccard coefficient, and can range from 0 to 1 depending on the degree of co-occurrence,

� is the number of co-occurrences of the two element types, � is the number of times the first element type occurs without the second, and � is the number of times the second element type occurs without the first. If the element types never occur together, � will equal 0 and the Jaccard coefficient will be 0, if the element types only occur together, the Jaccard coefficient will be 1, with intermediate values representing higher degrees of correlation as the value approaches 1.

For more details regarding the Bray-Curtis measure, see the Material and Methods portion of

Chapter 2. It is important to note that while both similarity measurements determine the relatedness of the elements, with 1 indicating elements that always occur together and 0 indicating elements that never occur together, the Bray-Curtis measure takes abundance data into account while the Jaccard coefficient does not. The use of binary versus absolute data has both advantages and disadvantages.

Von Bitter and Merrill (1998) discussed a possible danger in using similarity indices that take abundance data into account. They argued that if a conodont sheds specific elements through ontogeny, elements belonging to the same apparatus might not be expected to occur in similar quantities. This would make an attribute that would seem like an advantage, abundance counts, a significant disadvantage that could lead to incorrect reconstructions. They instead advocate the use of binary similarity indices, such as the Jaccard coefficient. However, it is important to note that this logic is built upon the assumption that conodonts shed elements during ontogeny, a concept that has yet to be sufficiently demonstrated. Similarity indices, such as the

Bray-Curtis measure, that utilize abundance data take advantage of all of the data available when assessing co-occurrence and can pick up on trends that a binary similarity index would otherwise miss. These data were treated to both a binary (Jaccard coefficient) and abundance (Bray-Curtis measure) cluster analysis. The use of both types of similarity indices allow for more patterns to be picked up by the absolute similarity index, which is especially important for a smaller dataset like that in this study, while using the more conservative binary similarity index to act as a check to the results.

1.4 Expanded Results

1.4.1 Morphologic groups

Nineteen morphologically distinct element types were recognized. These types were divided into larger groups that correspond to the position they most likely occupied in the apparatus (P1, P2, M, S0 or S). Five P1 element types were recognized (P1A, P1B, P1C, P1D, and

P1E), three P2 element types were recognized (P21, P22, and P23), two M element types were recognized (M1, and M2), three S0 types elements were recognized (S01, S02, and S03), and six S element types were recognized (S1, S2, S3, S5, S7, and S8). The elements are described using the anatomical notations proposed by Purnell et al. (2000). This has been chosen over the traditional description terminology because traditional terminology views the elements in isolation and does not account for the placement of the element within the apparatus. Since the apparatus is the focus of this study, anatomical notations have been used (Figures 1.2-1.7).

Figure 1.2: Platform element descriptive terminology showed on P1B (top view).

Anatomical notation has been used, with traditional notation in parentheses.

Figure 1.3: Platform element descriptive terminology shown on P1D (side view).

Anatomical notation has been used, with traditional notation in parentheses.

Figure 1.4: Blade element descriptive terminology shown on P21. Anatomical notation has been used, with traditional notation in parentheses.

Figure 1.5: Digyrate element descriptive terminology shown on M2. Anatomical notation has been used, with traditional notation in parentheses.

Figure 1.6: Alate element descriptive terminology shown on S02. Anatomical notation has been used, with traditional notation in parentheses.

Figure 1.7: Bipennate element descriptive terminology shown on S1. Anatomical notation has been used, with traditional notation in parentheses.

The P1 elements are differentiated from each other by a number of features, including the shape and placement of the basal cavity, presence of accessory denticles, and the overall style of denticulation (Figure 1.8). P1A and P1D both have a small, centrally located basal cavity that terminates before the dorsal tip of the element. P1D possesses one or more accessory denticles located on the right side of the platform, while these accessory denticles are absent in P1A.

Unlike P1A and P1D, P1B and P1C have a basal cavity that is shifted further dorsally and terminates at or near the dorsal tip of the element. P1B has a basal cavity that is strongly asymmetrical, and possesses a short parapet (composed of several fused denticles) on the caudal portion of the platform. However, P1C has a relatively symmetrical basal cavity, and lacks a parapet on the platform. P1E is the most distinctive P1 element, and can be diagnosed by its extremely brief dorsal process, its enlarged cusp, and its round, dorsally located basal cavity.

Figure 1.8: P1 element types.

The P2 elements are primarily differentiated from each other on morphology of the cusp

(Figure 1.9). The cusp is the denticle that directly overlies the apex of the basal cavity, and is commonly enlarged. In P21 and P23, the cusp in enlarged, however in P22 the cusp is not enlarged. The major difference between P21 and P23 is the angle of the cusp. P23 has a much more reclined cusp when compared to P21.

The M elements are primarily diagnosed based on the denticulation of the ventral process

(Figure 1.10). M1 possess an adenticulate ventral process, while M2 has denticulation on the ventral process.

Figure 1.9: P2 element types

Figure 1.10: M element types.

The S0 elements are differentiated from each other by characteristics of the lateral processes (Figure 1.11). S01 have short lateral processes, while both S02 and S03 have elongated lateral processes. S02 has lateral processes that have approximately a right angle between them, while S03 has lateral processes that have an acute angle between them. In addition S02 has a distinct bend on the aboral margin of the lateral processes, and a series of enlarged, flared denticles at the distal end of the lateral processes. S03, on the other hand, has lateral processes that are straight and possess denticles that are equant.

Figure 1.11: S0 element types.

The S elements are diagnosed based on multiple characteristics, including enlargement of the cusp, the type of denticulation on the rostral process, and the orientation of the rostral process

(Figure 1.12). S1 and S2 are the only S element types with a significantly enlarged cusp, and they are differentiated by the orientation of their rostral process. S1 has a slightly down-flexed rostral process, however S2 has a strongly down-flexed rostral process, to the point where the

processes ends directly underneath the cusp. The rest of the S elements do not have an obviously enlarged cusp, and are differentiated by their rostral processes. S3 has a rostral process that is deflected downward, and possesses a series of enlarged, fan-like denticles on the distal end of the process. Both S5 and S8 have rostral processes that are deflected inward, however the deflection of S5 is less pronounced, while the rostral process of S8 forms approximately a right angle with the caudal process. In addition, the S8 rostral process deflects downward at the distal end, forming a small hook. S7 has a diagnostically abbreviated rostral process, only possessing a few denticles.

Figure 1.12: S element types

For a more detailed description of each element type, please see the Systematic

Paleontology portion of Chapter Two. To avoid preempting the results in this section, the element types will be referred to by the alphanumeric names they were originally given.

However, in Chapter Two these element types are referred to by the species to which they are interpreted to belong. The synonymies between the two naming systems is as follows:

P1A = Bispathodus stabilis P1

P21 = Bispathodus stabilis P2

M1 = Bispathodus stabilis M

S02 = Bispathodus stabilis S0

S1 = Bispathodus stabilis S3/S4

S3 = Bispathodus stabilis S1/S2

P1B = Gnathodus texanus P1

P22 = Gnathodus texanus P2

P1C = Gnathodus homopunctatus P1

P23 = Gnathodus homopunctatus P2

M2 = Gnathodus homopunctatus M

S03 = Gnathodus homopunctatus S0

S2 = Gnathodus homopunctatus S3/S4

S8 = Gnathodus homopunctatus S1

S5 = Gnathodus homopunctatus S2

P1D = Bispathodus sp. A P1

P21 = Bispathodus sp. A P2

M1 = Bispathodus sp. A M

S02 = Bispathodus sp. A S0

S1 = Bispathodus sp. A S3/S4

S3 = Bispathodus sp. A S1/S2

P1E = Vogelgnathus gladiolus P1

S01 = Vogelgnathus gladiolus S0

S7 = Vogelgnathus gladiolus S

1.4.2 Element abundance and distribution

Overall, 1051 elements were identified from the 11 samples examined in this study. The element abundance and distribution are shown on Table 1.1.

Table 1.1: Element type abundance and distribution by sample number.

1.4.3 Thin Sections

Table 1.2: Thin section descriptions and conodont abundance by sample number. Some of the less common species are mentioned by name in the abundance column, however when not specified the abundance is referring primarily to the bispathodid elements.

Sample Conodont Abundance (extremely low <5, Rock Description Number low 5-20, medium 20-50, high 50-100, extremely high >100) 1028-17 Extremely low Silty, sponge spicules, (only one broken element found) calcareous fauna (echinoderms)

1028-18 High Tubular encrusting Vogelgnathus gladiolus foraminifera abundant, brown bitumen (high organic content), scattered amber pieces that could possibly be conodonts

1028-21 Medium Spicules, a lot of tubular encrusting foraminifera (½ mm long and 1/20 mm wide), organic matter present, angular silt ~3/40 mm

1028-22 Low Common ostracods and brachiopod spines, very fine carbonate mud, brachiopods filled w/ sparry calcite, echinoderm fragments, micro-gastropods, a few sponge spicules, rich in calcitic fossils, recrystallized

1028-23 Extremely high Spicules, angular silt, no irregular tubes (interpreted as encrusting tubular foraminifera), dark micro- bioclastic

Sample Conodont Abundance (extremely low <5, Rock Description Number low 5-20, medium 20-50, high 50-100, extremely high >100) 1028-25 Extremely high Sponge spicules, tubular encrusting foraminifera (½ mm long and 1/20 mm wide), organic matter present, angular silt

1028-26 Extremely high irregular tubular forams very Gnathodus cf. homopunctatus abundant, finer with smaller percentage of bioclasts, angular silt present

1028-27 Low spicules, angular silt, small bioclasts, brachiopod spines, carbonate mud matrix, bitumen staining (source rock) burrows? (large rounded clasts or perhaps fecal pellets) some echinoderm bioclasts (few, microporous), some ostracodes

Figure 1.13: Photomicrographs of thin sections taken under a transmitted light microscope, showing general lithologic characteristics. All images taken in plane polarized light.

1.4.4 Empirical Observations

While counting these elements and plotting their distributions, empirical observations were made regarding elements that occurred in the same samples and in similar quantities. Four recurrent element distributions were noted. The first distribution involves elements that displayed high abundances in samples 1028-21 to 1028-26. The second distribution involves elements that show a dramatic peak in abundance in sample 1028-26. The third distribution involves elements that displayed low abundance overall, and had a small peak in abundance in sample 1028-18. The final distribution contains elements that have low abundance overall and never show any true peaks in abundance, but do occur in samples 1028-23 through 1028-27.

The element types that display the first distribution, which was characterized by high abundance in samples 1028-21 through 1028-26, include P1A, P1D, P21, M1, S02, S1, and S3

(Figure 1.13; Figure 1.14). It should be noted that two P1 element types are included in this distribution, which would be atypical of an ozarkodinid apparatus. P1A and P1D have slightly different distributions, with P1A occurring in highest abundance in samples 1028-26 and 1028-

25, and P1D occurring in highest abundance in sample 1028-23. The reason these two element types are included together is because the rest of the element types in this distribution appear to be show a combination of the distributions of P1A and P1D. For example, P21 has high abundances in 1028-26, 1028-25, and 1028-23, a combination of the highest distributions of P1A and P1D. The interpretation is that these two P1 element types came from different species, however these species were closely related and possessed identical apparatuses other than their

P1 morphology. This is consistent with the morphologic similarity seen in P1A and P1D, and with subsequent identifications of P1A and P1D as belonging to the same genus.

31 Distribuon One

P1 A P1 D P2 1 S0 2 M1 S 1 S 3 60

30 Abundance 20

0 18 19 20 21 22 23 24 25 26 27 28 Sample Number

Figure 1.14: Element types that display distribution one, which is characterized by high element abundance in samples 1028-21 through 1028-26. The Y-axis (labeled

“Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18

= 1028-18).

Figure 1.15 (previous page): All element types, with elements that displayed distribution one in bold. Distribution one corresponds to elements that show a high abundance in samples 1028-21 through 1028-26. The Y-axis (labeled “Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18 = 1028-18).

The element types that display the second distribution include P1C, P23, M2, S03, S2, S8, and S5 (Figure 1.15; Figure 1.16). This distribution is characterized by a dramatic spike in element abundance in sample 1028-26, and is the easiest of the distributions to recognize. The only element that has been placed in this group that is somewhat questionable is S5. This is because, while S5 does exhibit an abundance peak in sample 1028-26, it is not as dramatic as the peak seen in the other samples. It is interpreted that the elements placed in this group all belonged to the same species, which was dominant during the deposition of sample 1028-26.

Distribuon Two

P1 C P2 3 S0 3 M 2 S 2 S 8 "S 5"

100 90 80 70 60 50

Abundance 40 30 20 10 0 18 19 20 21 22 23 24 25 26 27 28 Sample Number

Figure 1.16: Element types that display distribution two. Distribution two corresponds to element types that occur in low abundance throughout the samples and show a pronounced abundance spike in sample 1028-26. The Y-axis (labeled “Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18 = 1028-18).

Figure 1.17 (previous page): All element types, with elements displaying distribution two highlighted. Distribution two is characterized by elements having a low abundance in all the samples except for sample 1028-26, in which elements have a pronounced abundance spike. The Y-axis (labeled “Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18 = 1028-18).

The element types that display the third distribution include P1E, S01, and S7 (Figure

1.17; Figure 1.18). These elements are only commonly found in sample 1028-18, with very few scattered occurrences in other samples. The interpretation is that these elements represent a partial apparatus of a species. The apparent lack of the rest of the typical ozarkodinid apparatus for this species may be due to the low abundance of this species, or the small size of the elements belonging to this species.

Distribuon Three

P1 E S0 1 S 7

Abundance 6

0 18 19 20 21 22 23 24 25 26 27 28 Sample Number

Figure 1.18: Element types that display distribution three. Distribution three is characterized by elements have low abundance overall, with occurrences in sample 1028-

18. The Y-axis (labeled “Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18 = 1028-18).

Figure 1.19: Element types with distribution three elements bolded. Distribution three is characterized by elements have low abundance overall, with occurrences in sample 1028-

The element types that display the fourth distribution include P1B and P22 (Figure 1.19;

Figure 1.20). Both of these elements were extremely rare, and have their highest abundance in sample 1028-26. The interpretation is that these elements represent a partial apparatus of a

species, however due to the low abundance of these elements and lack of a significant abundance spike in any samples, this interpretation is tenuous. The apparent lack of the rest of the apparatus may again be due to the low abundance of this species.

Distribuon Four

P1 B P2 2

2 Abundance

0 18 19 20 21 22 23 24 25 26 27 28 Sample Number

Figure 1.20: Element types that display the distribution four. Distribution four is characterized by elements having low abundance overall, with occurrences in samples

1028-24 through 1028-27. The Y-axis (labeled “Abundance”) refers to an absolute count rather than a percentage, and the numbers on the X-axis correspond to the samples numbers with 1028 attached to the beginning (i.e. 18 = 1028-18).

Figure 1.21: Element types with distribution four elements bolded. Distribution four is characterized by elements having low abundance overall, with occurrences in samples

Overall, five partial to complete apparatuses were recognized via empirical observations of element distribution and abundance. Two of these apparatuses (those belonging to P1A and

P1D) have been interpreted as identical, excepting the P1 elements. These empirical observations

were made to gain an understanding of the raw data prior to any quantitative analyses being performed, to compare the quantitative results to those produced qualitatively.

1.4.5 Rarefaction

Rarefaction was run on all of the samples that had more than one conodont species. The only sample that appeared to still be increasing in the number of taxa is sample 1028-24. The cluster analyses were run twice, once with all of the samples and once excluding the samples that contained only one conodont species and sample 1028-24. The results of the cluster analyses using all of the data and the cluster analyses that excluded data based on the rarefaction results were identical. Because the rarefaction did not alter the results of the cluster analysis, it was chosen to use the original element counts rather than an altered dataset.

1.4.6 Cluster Analysis

Running cluster analysis using the Jaccard similarity coefficient produces four distinct clusters of elements. Each of these clusters contains P1 elements, with three out of the four clusters containing one P1 element type and one cluster containing two types of P1 elements.

The first cluster produced by this analysis contains P1 Type B, P2 Type 2, and S0 Type 3

(Figure 1.21). This cluster does not contain all the element types found in an ozarkodinid apparatus, representing a partial apparatus reconstruction. This may be due to the low abundance of these elements.

The second cluster contains P1 Type A, P1 Type D, P2 Type 1, M Type 1, M Type 2, S0

Type 1, S Type 1, and S Type 3. This cluster contains the P1 elements of both Bispathodus stabilis and Bispathodus sp. A. These P1 elements are most likely clustering together because

their apparatuses contain the same non-platform elements, and therefore this cluster represents a mixture of biologic and taxonomic associations. Another interpretation could be that these species are clustering together because they occupied the same paleoenvironment, however since these species belong to the same genus, the taxonomic association is favoured.

Figure 1.22: Cluster analysis results using the Jaccard Coefficient

Only two M element morphologies were distinguished in this study, with both clustering in the second cluster. This could indicate the M elements belonging to the other reconstructed apparatuses were not found, the other species reconstructed here have M elements so similar as

to be indistinguishable, or an insufficiency in the binary nature of the Jaccard Coefficient. It is most likely a combination of the last two factors. It is possible that using morphometrics, subtle differences could be picked out to differentiate more M element morphologies, however such an analysis would be outside the scope of the present study.

The third cluster produced in this analysis contains P1 Type C, P2 Type 3, S0 Type 2, S

Type 2, S Type 5, and S Type 8. The last cluster contains P1 Type E and S Type 7.

A second cluster analysis was run using the Brays-Curtis similarity index instead of the

Jaccard coefficient (Figure 1.22). Unlike the Jaccard coefficient, the Brays-Curtis similarity index takes the abundance of elements found in each sample into account when assigning similarity. This cluster analysis, like the previous analysis, produces five clusters, three of which contain one P1 type and one that contains two bispathodid P1 elements, however one cluster produced in this analysis does not contain any P1 elements.

Figure 1.23: Cluster analysis results using the Bray-Curtis similarity index

1.4.7 Biostratigraphy and Paleoenvironment

The conodont species found in the Hart River Formation are indicative of the age and paleoenvironment of the formation. The conodont zonation and age ranges used here are those found in Higgins and Austin, (1985), combined with information from Sweet, (1988) and

Gradstein et al. (2012). The samples yielded Bispathodus sp. A, Bispathodus stabilis (Branson and Mehl, 1934), Gnathodus texanus Roundy 1926, Gnathodus homopunctatus Ziegler 1960, and Vogelgnathus gladiolus Purnell and von Bitter 1992.

Bispathodus stabilis has a known range from the lower Palmatolepis marginifera conodont zone (middle Famennian) to the upper portion of the Gnathodus texanus zone (lower

Visean; Figure 1.24). Gnathodus texanus appears the base of the Gnathodus texanus zone (lower

Visean) and ranges up to the top of the Gnathodus bilineatus conodont zone (upper Visean;

Figure 1.24). Gnathodus homopunctatus ranges from the base of the Gnathodus texanus conodont zone (lower Visean) to the upper portion of the Kladognathus-Gnathodus girtyi simplex conodont zone (lower Namurian; Figure 1.24). The lower boundary of the Vogelgnathus gladiolus range is uncertain, however it has been found in the Chadian, through the Arundian, and into the Holkerian (British Dinantian stages; Purnell and von Bitter, 1992; Figure 1.24).

These stages comprise the lower half of the Visean and correlate to below and above the lower boundary of the Gnathodus texanus conodont zone (Barham et al., 2014; Purnell and von Bitter,

1992). The co-occurance of these species indicate that the Hart River Formation falls into the

Gnathodus texanus conodont zone, making it early Visean in age (Figure 1.24). This differs slightly from the late Visean and early Serpukhovian age determined by Bamber et al. (1989).

Bamber et al. (1989) used conodonts to make this age determination, and it is important to note that these are the same specimens that are examined in this study. The major difference that indicates a late Visean age in this study, rather than early Serpukovian, is the identification of what was called Rachistognathus prolixus by Bamber et al. (1989) as Bispathodus sp. A.

The conodont species found in the Hart River Formation also indicate a certain paleoenvironment. The vast majority of conodonts recovered from the Hart River Formation belong to the genus Bispathodus. While there are some specimens of Gnathodus texanus, these specimens occur only in a few samples and in very small quantities. Likewise, the specimens of

Gnathodus homopunctatus only occur in two samples, although they can be abundant when

found. Conversely, Bispathodus stabilis or Bispathodus sp. A occur in almost every sample and often in abundance. Bispathodus species have been found in deep, basinal environments in

Mississippian deposits of the Deseret Basin, which occurs along the western portion of the

United States (Sweet, 1988; Figure 1.23). In the same basin Gnathodus species were found in association with slope deposits (Sweet, 1988). The dominance of Bispathodus indicates a “deep” basinal depositional environment. Of course deep is a relative term and it could also mean most offshore and a particular depth is not interpreted. The occasional occurrences of Gnathodus could represent periods of marine regression or transportation of slope material into the basin.

Figure: 1.24: Ranges of conodont species recovered from the Hart River Formation, with the interpreted age of the Hart River Formation shaded in green. Abbreviations: S. –

Siphonodella, G. – Gnathodus, L. – Lochriea, B. – Bispathodus, V. – Vogelgnathus. Dashed lines indicate probable age range.

1.5 Discussion

Both cluster analyses produced five clusters of elements that correspond to hypothesized apparatus reconstructions. While the clusters produced by these analyses were similar, there are some differences in apparatus composition produced by the different similarity indices.

Both analyses clustered P1B and P22 together, making this associate strong. These elements were not clustered with any other elements in the Bray-Curtis analysis, however the

Jaccard cluster analysis also included S0 3 with these elements. The results of the Bray-Curtis analysis are favoured here, due to the dramatic spike in abundance in sample 1028-26. While it is true that both S03 and P22 only occur in sample 1028-26, 1028-26 contains 12 S03 elements

(which are the most fragile and rarest in the apparatus) and only 3 P22 elements (which are relatively robust and twice as abundant as the S0 element in the apparatus). This is not the ratio of P2 to S0 elements expected if these elements came from the same species. The absence in other samples and dramatic peak of abundance at 1028-26 displayed by S0 3 is more in line with the distribution of elements seen in cluster P1C.

In both analyses Bispathodus stabilis P1 and Bispathodus sp. A P1 clustered together.

This is interpreted as being due to a similarity in apparatus composition between these two species and the occupation of a similar paleoenvironment, with the main difference being the morphology of their P1 elements. The elements associated with these P1 elements in both analyses are P21, M1, S1, and S3. The difference is that the Jaccard cluster analysis also includes S01, and M2 in the bispathodid apparatus. S01 will be excluded from the bispathodid apparatus, as it only occurs in a few samples, and only in high abundance in sample 1028-18

(which does not correspond to a peak abundance of the other elements in this cluster). M2 will

also be excluded from this apparatus reconstruction due to the dramatic abundance spike in sample 1028-26, which correlates to cluster P1C.

In addition, while neither cluster analysis produced this result, S02 should be included in the bispathodid apparatus. S02 occurs in samples 1028-23, 1028-25, and 1028-26. The abundance of the elements decreases up section, with the highest being in sample 1028-23. The abundance of S02 is relatively low when compared to the number of other element types recovered, however when compared to the abundance of the other S0 elements, the number of identifiable S02 elements is relatively high. This apparent low abundance may be due to the fact that these elements are never as abundant as the other elements in the apparatus (1 out of 15 elements), and this element type is particularly hard to identify if broken (diagnostic features are at the end of the denticles). Indeed, many unidentifiable S0 elements were found in other samples that may have conformed to this morphology before breakage. Due to this, S02 is hypothesized to cluster with the bispathodid group of elements if the original abundance of S0 elements were corrected for, and if more of the broken S0 elements found throughout the samples could be identified.

P1C clusters with P23, S2, and S8 in both analyses. The Jaccard cluster analysis places

S02, and S5 in this cluster. S02 is placed in the bispathodid apparatus for reasons discussed above, and S5 is included in this apparatus reconstruction. The Brays-Curtis analysis places M2, and S03 in this cluster. Both of these elements are included in this apparatus reconstruction, due to a pronounced spike in abundance in sample 1028-26, which is characteristic of this cluster and seen in both of these element types.

The last cluster produced by these analyses contains P1E, and S7. The Brays-Curtis analysis also placed S01 in this cluster, while the Jaccard analysis did not. Since S01 only occurs

in abundance in sample 1028-18 (same as P1E and S7), it will be included in this apparatus reconstruction

1.5.1 Combined Cluster Analysis Results:

Black text below represents elements that were clustered together in both analyses and therefore are the strongest associations. Blue text below represents elements that were clustered in the presented location in only one of the analyses, indicating a more uncertain association.

Red text below represents elements that were not clustered in the present location in either cluster analysis, but were instead assigned placement based on empirical observations. These are by nature the most uncertain associations.

Gnathodus texanus apparatus reconstruction

Gnathodus texanus P1 element (P1 Type B)

Gnathodus texanus P2 element (P2 Type 2)

Bispathodus stabilis apparatus reconstruction

Bispathodus stabilis P1 element (P1 Type A)

Bispathodus P2 element (P2 Type 1)

Bispathodus M element (M Type 1)

Bispathodus S0 element (S0 Type 2)

Bispathodus S1/2 element (S Type 1)

Bispathodus S3/4 element (S Type 3)

Bispathodus aculeatus aculeatus apparatus reconstruction

Bispathodus sp. A P1 element (P1 Type D)

Bispathodus P2 element (P2 Type 1)

Bispathodus M element (M Type 1)

Bisapthodus S0 element (S0 Type 2)

Bispathodus S1/2 element (S Type 1)

Bispathodus S3/4 element (S Type 3)

Gnathodus homopunctatus apparatus reconstruction

Gnathodus homopunctatus P1 element (P1 Type C)

Gnathodus homopunctatus P2 element (P2 Type 3)

Gnathodus homopunctatus M element (M Type 2)

Gnathodus homopunctatus S0 element (S0 Type 3)

Gnathodus homopunctatus S1 element (S Type 2)

Gnathodus homopunctatus S2 element (S Type 8)

Gnathodus homopunctatus S3/4 element (S Type 5)

Vogelgnathus gladiolus apparatus reconstruction

Vogelgnathus gladiolus P1 element (P1 Type E)

Vogelgnathus gladiolus S0 element (S0 Type 1)

Vogelgnathus gladiolus S element (S Type 7)

1.6 Role of the student

Dr. Wayne Bamber, formerly of the Geological Survey of Canada (GSC), collected the conodont samples examined in this study from the Hart River Formation. Staff at the Geological

Survey of Canada extracted the conodonts from the host rock using standard dissolution techniques and picked the residue for conodont elements. The conodonts were then sent to Dr.

Charles Henderson for identification, the results of which can be found in Bamber et al. (1989).

I imaged the conodont elements using a Scanning Electron Microscope with the assistance of

Michael Schoel, of the University of Calgary. The rock samples were cut by myself, and then made into thin sections by Mickey Horvath, of the University of Calgary.

I carried out the rest of the work presented here. This includes designating morphologic groups, counting elements, making empirical observations, performing the rarefaction and cluster analyses, cutting rock for thin sections, and identifying species. Dr. Charles Henderson assisted in the descriptions of the thin sections and species identifications. In addition, Dr.

Henderson provided valuable feedback regarding all the steps performed by myself and provided edits towards the completion of this manuscript.

Chapter Two: Conodont Apparatus Reconstruction Conodont apparatus reconstruction from the Middle Mississippian

Hart River Formation, northern Yukon Territory, Canada

Amanda Lanik1 and Charles M. Henderson2

1Department of Geoscience, University of Calgary, Calgary, Alberta T2N 1N4

2Department of Geoscience, University of Calgary, Calgary, Alberta T2N 1N4

2.1 Introduction

When Pander first described conodonts in 1856, species were established based on the morphology of individual elements. This practice has come to be referred to as “form taxonomy”, and was adopted by many of the early pioneers of conodont studies. This was done despite the uncertainty as to whether the conodont animal possessed a single element, multiple elements of a single morphology, or multiple elements of differing morphologies. Form taxonomy would be an appropriate basis for species if one of the first two options proved true.

However, subsequent findings have shown that conodonts possessed a feeding apparatus that contained elements with a variety of differing morphologies (Briggs et al., 1983).

The possibility that conodonts possessed elements of differing morphologies was proposed, if not fully accepted, by conodont workers as early as the 19th century. Hinde (1879)

was the first to propose that clusters of elements found along bedding planes belong to individual animals. Both Schmidt (1934) and Scott (1934) described Carboniferous conodont bedding plane assemblages, interpreting these as the skeletal remains of individual specimens. Despite these early publications suggesting the conodont species concept might be more complex than originally thought, the shift from form taxonomy to a biologic taxonomy that encompasses all of the elements within the apparatus (termed “multi-element taxonomy”) is still taking place. One reason for the difficulty in establishing multi-element taxonomy is the phenomenon found in many samples of disjunct elements from the Late Paleozoic called platform-overrepresentation

(or ramiform-underrepresentation).

Based on natural assemblages it has been proposed that conodonts of the order

Ozarkodinida have apparatuses composed of 15 elements, 11 of which display a ramiform, or bar, morphology (Purnell et al., 2010). Despite this apparent preponderance of ramiform elements in the apparatus, many Late Paleozoic samples of disjunct elements contain few ramiform elements and are instead dominated by platform-type elements. This phenomenon has been attributed to various causes, both taphonomic and biological (see Purnell and Donoghue,

2005 for an overview). One suggestion, put forward by Merrill and Powell (1980), is that the number of elements in an apparatus may change throughout the conodont’s life cycle.

Merrill and Powell (1980) proposed that juvenile (smallest elements in a growth series) ozarkodinid conodonts possessed a complete 15-element apparatus, while adult conodonts lost their ramiform elements via resorption, resulting in an apparatus composed of only platform elements. This conclusion was based primarily on a sampled horizon that yielded juvenile platform elements and abundant ramiform elements, while other samples from the same section containing “adult” platform elements showed significant ramiform-underrepresentation.

Zhuravlev (1999), figured partially resorbed ramiform elements, lending support to Merrill and

Powel’s interpretation. However, it is difficult to verify that these structures were formed while the conodont was alive and are not instead the result of diagenesis or the extraction process.

Other authors have argued that there is no evidence to suggest that the number of elements in a conodont apparatus changed during ontogeny (Purnell, 1994). The most compelling evidence against Merrill and Powel’s suggestion is the abundance of natural assemblages that contain “adult” platform elements and still retain their full ramiform set. In addition, wear patterns studied by Donoghue and Purnell (1998) indicate that elements were periodically damaged and repaired, suggesting that conodonts did not shed elements. As demonstrated by von Bitter and Merrill (1990), this question of whether conodont elements were shed and/or resorbed during ontogeny is vital to any study that attempts to use statistical methods of apparatus reconstruction, since element counts are often used as a proxy for the number of individuals in a given sample. Using a similarity index that simplifies these data to present/absent values can partially counteract this issue. However, present/absent indices work best on large sets of data and only 11 samples were analyzed from the Hart River Formation. In addition, since the ontogenetic shedding of elements has not been sufficiently demonstrated, there is no reason to assume the species recovered from the Hart River Formation altered their apparatus during ontogeny. Consequently, a more robust similarity index that utilizes absolute counts was used.

Conodont apparatuses can be reconstructed either by direct observation of bedding plane assemblages or fused clusters, or statistical analyses of disjunct element associations. The direct observation method is obviously superior as there is far less ambiguity concerning which elements occur together, and the position and relative size of the elements in a single apparatus

can be determined. However, bedding plane assemblages and fused clusters are relatively rare and not evenly distributed stratigraphically or geographically, so other methods of reconstruction must be employed.

Conodont workers have approached apparatus reconstruction from discrete sample sets in multiple ways. The simplest way is by examining a sample that contains only one species, so all the non-platform elements can be assigned to that species (Over, 1992; Sandberg and Gutschick,

1984). Other workers have used previously proposed apparatuses to assign ramiform elements to known multi-element species, leaving only elements of the unknown species remaining (Atakul-

Ozdemir et al., 2012). However, this method can only be used when all other co-occurring species have firmly established apparatuses. Finally, statistical methods, such as cluster analysis, have been used as early as the 1960’s to analyze large groups of data and pick out recurrent element groups (Kohut, 1969; Horowitz and Rexroad, 1982). This method does not rely on having monospecific samples, nor does it rely on samples that primarily contain species with known apparatuses, making it the chosen method of apparatus reconstruction in this study.

This study examines conodont elements that were collected from the Carboniferous Hart

River Formation, found in the Yukon Territory. The elements recovered from these samples are abundant, well-preserved, display minimal platform-overrepresentation, and have a relatively low diversity, making them ideal for statistical apparatus reconstruction. Running cluster analysis on these samples produces 5 partial to whole apparatus reconstructions, belonging to the species Bispathodus sp. A, Bispathodus stabilis morphotype 2, Gnathodus homopunctatus,

Gnathodus texanus, and Vogelgnathus gladiolus.

Bispathodus stabilis, one of the species reconstructed in this study, is a long ranging taxon (Famennian-Visean) with a relatively simple platform morphology. Probably due to these

characteristics, Bispathodus stabilis has been hypothesized to be the ancestor of multiple

Carboniferous genera. Sweet (1988) suggested that Bispathodus stabilis gave rise to the Family

Gnathodontidae, which includes the genera Protognathodus and Gnathodus. It has also been suggested that Bispathodus stabilis gave rise to the genus Lochriea (Somerville, 2008).

However, these proposed evolutionary relationships are mainly based on observed changes in platform morphology only and do not take the rest of the elements into account.

Recent studies have been conducted that test the evolutionary relationships of

Bispathodus stabilis using the morphology of the entire apparatus and a cladistic approach.

Donoghue et al. (2008) performed a cladistic analysis of many “complex” conodonts, including the genus Bispathodus and its proposed descendent genera. Their analysis found that

Bispathodus is a stem taxon of the genera Gnathodus and Idiognathodus, however Lochriea was not closely related to any of these genera. Instead, Donoghue et al. (2008) found Lochriea to be more closely related to the genera Sweetognathus and Clydagnathus. Protognathodus was not included in this study.

A portion of the dataset used by Donoghue et al. (2008) was expanded by Atakul-

Özdemir et al. (2012) to test the evolutionary relationship between Bispathodus stabilis and the genus Lochriea. This was facilitated in part by their new apparatus reconstruction for the species originally called Gnathodus commutatus punctatus, which they reassigned as Lochriea homopunctatus (Atakul- Özdemir et al., 2012). This species has a complex history, having been referred to as Gnathodus homopunctatus, Paragnathodus homopunctatus, Pseudognathodus homopunctatus, or Lochriea homopunctatus by various authors at different times (see synonymy portion of the Systematic Paleontology). Atakul-Özdemir et al. (2012) combined their newly reconstructed Lochriea homopunctatus apparatus with data from the Bispathodus stabilis

apparatus reconstructed by Over (1992). These data were added to the subset of the Donoghue et al. (2008) dataset and a cladistic analysis was run. The results led the authors to conclude that

Bispathodus stabilis did not give rise to the genus Lochriea (Atakul-Özdemir et al., 2012). Since this study reconstructs the apparatuses for both Bispathodus stabilis and what is here called

Gnathodus homopunctatus (Lochriea homopunctatus of Atakul-Özdemir et al., 2012), the results presented here aid in elucidating the relationships of these key taxa.

2.1.1 Study area.—

The Hart River Formation is a package of primarily fine-grained, spicular limestone that crops out in southern Eagle Plain, northern Yukon Territory (Graham, 1975). Overlying the Ford Lake

Formation, the uppermost portion of the Innuitian-sourced Imperial Assemblage, the Hart River

Formation represents a return of passive margin sedimentation after the Ellesmerian orogeny

(Garzione et al., 1997). The depositional environment of the Hart River Formation is interpreted to be upper to middle slope facies that transition into lower slope to basinal facies towards the southwest (Gordey et al., 1991). The samples examined in this study were collected from the southeastern portion of Eagle Plain, from the Peel River section described by Bamber and

Waterhouse (1971; Figure 1).

Previous paleontological studies have been conducted on the Hart River Formation

(Bamber and Waterhouse, 1971; Bamber et al., 1989). Bamber and Waterhouse (1971) assigned the Hart River Formation to primarily late Visean and early Namurian, occasionally ranging up into the Moscovian based on brachiopod, ammonoid, and foraminifer data. Bamber et al. (1989) also did biostratigraphic work on the Hart River Formation, using brachiopods, foraminifera, conodonts, ammonoids, and palynomorphs. The results of this study assigned the Hart River

Formation to the middle to late Visean and early Serpukhovian. The conodonts found included

Gnathodus texanus, Gnathodus pseudosemiglaber (juveniles), Bispathodus stabilis, and

Rachistognathus prolixus, indicating a late Visean age (Bamber et al., 1989). The conodonts examined by C.M. Henderson for the Bamber et al. (1989) paper are the same elements examined in this study.

Figure 1: Map showing the extent of Carboniferous and Permian outcrops in the Yukon

Territory. Circled in red is the area where the samples were collected from the Hart River

Formation along the Peel River in the southeastern part of Eagle Plain (from Bamber and

Waterhouse, 1971).

2.2 Materials and methods

The samples examined here were collected by Dr. Wayne Bamber and processed at the

Geological Survey of Canada (GSC) using standard conodont processing techniques. For this study the conodont elements were divided into groups based on morphology and counted. To avoid counting multiple fragments of the same element, only elements with more than half of the basal cavity were counted. The 11 samples produced 1051 elements that conform to 21 different morphologies (Table 1).

Table 1: Abundance and distribution of the elements found in the Hart River Formation Samples.

Since all of the P1 elements recovered belong to the order Ozarkodinida, the standard 15- element ozarkodinid apparatus structure has been assumed. In addition, the anatomical notation

for the Ozarkodinida apparatus proposed by Purnell et al. (2000) has been followed. Of the 1051 elements found, 216 are platform elements (P1), 161 are blade elements (P2), 175 are digyrate elements (M), 58 are alate elements (S0), and 441 are bipennate elements (S). Despite the abundance of non-platform elements, these samples are still slightly platform-overrepresented.

However, this overrepresentation is far less significant than most Late Paleozoic conodont samples and the overrepresentation that is seen here is likely a product of the processing and counting processes. The slight overrepresentation in these samples is most likely due to breakages of the more fragile ramiform elements and the greater difficulty in identifying and counting the smaller ramiform basal cavities (especially in the case of the S elements).

Due to the minimal platform overrepresentation, the presence of a variety of element shapes and sizes, the excellent preservation of the elements, and the sedimentology, significant post-depositional taphonomic bias is unlikely. In addition, these samples display high abundances of conodont elements, but low diversity. This means that statistical methods can be used to assess the co-occurrence of the elements, which is interpreted as representing the original apparatus composition. Cluster analysis was used to assess the co-occurrence of the disjunct elements. In addition, during the counting process some element associations were noted purely through empirical observations. These associations will subsequently be compared with the associations produced via cluster analysis, highlighting the strengths and limitations of both methods.

Cluster analysis is a method that uses a chosen similarity index to construct a hierarchical tree, with groups and subgroups corresponding to relatedness (Hammer and Harper, 2008). In this study the Bray-Curtis measure has been used to determine similarity among the element occurrences. The Bray-Curtis measure for abundance data is as follows:

! �!" − �!" �!" = 1 − ! �!" + �!" djk represents the Bray-Curtis similarity between two samples j and k, each defined by a set of attributes xji and xki (Michie, 1982). In this case the attributes represent the abundance of various elements found each sample. The Bray-Curtis measure is a dissimilarity coefficient, but since it is being subtracted by 1 the Bray-Curtis similarity is given, with lower values representing element types that are not closely related, with relatedness increasing as the value approaches one.

The cluster analysis produces a dendogram, showing the groups of elements and how closely they are related. These recurrent groups can represent taphonomic, environmental, taxonomic, or biological associations. Taphonomic processes, such as sorting, could cause elements to occur in the same samples even if they were not originally deposited together. An environmental association can be found when elements did not belong to the same species, but different species that occupied the same paleoenvironment, consequently causing these elements to be preserved in the same samples. A “taxonomic” association, unlike the other associations, is a result of the way cluster analysis works rather than the elements being consistently found together. If two species share many elements that are morphologically identical, however never occur in the sample, they may cluster together purely because they are always found with the same elements. It is termed “taxonomic” because species that share many of the same elements are typically related. The final association is a biological association, which occurs when elements that belonged to the same animal are deposited in the same place when that animal dies.

The majority of the groups produced in this cluster analysis are interpreted as biological

associations (belonging to the same apparatus), however some of the clusters produced may be due to environmental or taxonomic associations.

2.3 Results

A cluster analysis was run using the Bray-Curtis measure, which takes the abundance of elements found in each sample into account when assigning similarity. This cluster analysis produced five clusters, three of which contain one P1 type and one that contains two bispathodid

P1 elements, however one cluster was produced that does not contain any P1 elements (Figure 2).

Figure 2: Cluster analysis results using the Bray-Curtis similarity index.

2.4 Discussion

The cluster analysis produced five clusters of elements that correspond to four hypothesized apparatus reconstructions. The results of the cluster analysis were combined with empirical observations made while counting to produce the apparatus reconstructions. These partial/full apparatus reconstructions belong to the species Bispathodus sp. A, Bispathodus stabilis,

Gnathodus texanus, Gnathodus homopunctatus, and Vogelgnathus gladiolus. These species identifications are based on the morphology of the P1 element in combination with the rest of the apparatus, especially in cases where previous apparatuses for that species have been described.

For further discussion of the species identifications, see the Systematic Paleontology portion of this paper.

The analysis clustered Gnathodus texanus P1 and P2 together without any other elements.

This cluster corresponds with the empirical observations made about these elements, since they both occur in low abundance throughout the samples and are found primarily in sample 1028-26.

Since this cluster only contains one P1 element and one P2 element, it represents a partial apparatus reconstruction. The rest of the apparatus was likely not recovered due to the low abundance of these elements.

Bispathodus stabilis P1 and Bispathodus sp. A P1 belong to the same cluster, despite them both being P1 elements. Since the standard 15-element ozarkondinid apparatus is assumed for all the species in this study, having two P1 elements in one cluster indicates that this cluster may not represent purely anatomical associations. The only explanation that could account for the occurrence of two morphologically distinct P1 elements in a cluster representing an anatomical association would be that the species has an asymmetric apparatus, with the sinistral P1 element being morphologically distinct from the dextral P1 element. However, since neither Bispathodus

stabilis P1 nor Bispathodus sp. P1 is represented by exclusively dextral or sinistral elements, this interpretation can be ruled out. Two other possibilities that these two elements are clustering together are for environmental or taxonomic reasons. A taxonomic association is favoured over the environmental interpretation because both P1 elements belong to the genus Bispathodus, and it is expected that the apparatus for two species of the same genus would be very similar. This suggests that, except for the P1 element morphology, the apparatus for these two species is only distinctive at the genus level.

The other elements clustered with Bispathodus stabilis P1 and Bispathodus sp. A P1 are

Bispathodus P2, Bispathodus M, Bispathodus S1/2, and Bispathodus S3/4. In addition, while the cluster analysis did not cluster it together as closely, Bispathodus S0 is included in the bispathodid apparatus. Bispathodus S0 occurs clustered together with Gnathodus homopunctatus

S3/4, which is weakly related to both the Bispathodus cluster and the Gnathodus homopunctatus cluster. Bispathodus S0 is found in samples 1028-23, 1028-25, and 1028-26. The abundance of the elements decreases up section, with the highest abundance occurring in sample 1028-23. The abundance of Bispathodus S0 is relatively low when compared to the number of other element types recovered, however when compared to the abundance of the other S0 elements, the number of identifiable Bispathodus S0 elements is high. This apparent low abundance is likely due to these elements never being as abundant as the other elements in the apparatus, comprising just 1 out of 15 elements in an apparatus, whereas the other element types typically comprise 2 to 4 of the 15 elements. In addition, this element type is difficult to identify if broken since the diagnostic features are at the end of the processes. Many unidentifiable S0 elements were found in other samples that may have conformed to this morphology before breakage. Due to this,

Bispathodus S0 is hypothesized to belong with the bispathodid apparatus if the original

abundance of S0 elements were corrected for, and if more of the broken S0 elements found throughout the samples could be identified.

Gnathodus homopunctatus P1 clusters with Gnathodus homopunctatus P2, Gnathodus homopunctatus S1, Gnathodus homopunctatus S2, Gnathodus homopunctatus S3/4, Gnathodus homopunctatus M, and Gnathodus hompunctatus S0. These elements all have a pronounced spike in abundance in sample 1028-26, and are relatively rare in the other samples. This abundance peak makes this cluster easier to pick out empirically, and the empirical observations line up well with the results produced by the cluster analysis. The only element that has been included in this apparatus that was not found in this cluster is Gnathodus homopunctatus S3/4.

Gnathodus homopunctatus S3/4 and Bispathodus S0 were both part of a small cluster that contained no other elements and was weakly associated with both the Bispathodus cluster and the Gnathodus homopunctatus cluster. Bispathodus S0 is placed in the Bispathodus apparatus, while Gnathodus homopunctatus S3/4 is placed in the Gnathodus homopunctatus apparatus. This has been done because Gnathodus homopunctatus S3/4, like the other elements in this cluster, can be found in low abundance in samples 1028-23, and 1028-25. While Gnathodus homopunctatus

S3/4 does occur in sample 1028-26, it does not show the dramatic abundance spike shown by other elements placed in this apparatus. Due to this, Gnathodus homopunctatus S3/4 should not be regarded as strong an association as the rest of the elements assigned to this apparatus.

The last cluster produced by this analysis contains Vogelgnathus gladiolus P1,

Vogelgnathus gladiolus S, and Vogelgnathus gladiolus S0. Like the first cluster discussed, this cluster does not contain a full complement of element types expected in a complete ozarkodinid apparatus, and is therefore a partial apparatus reconstruction. Again, this is most likely due to

the low abundance of these element types recovered from the samples, and possibly also due to the extremely small size of the elements.

2.5 Systematic paleontology

Five species from three genera were recovered from the Hart River Formation. These species have been described using anatomical notation proposed by Purnell et al. (2000), in combination with the terminology outlined by Sweet (1981). The anatomical notation was chosen over traditional descriptive notation because traditional notation views the elements in isolation and examining the conodont apparatus as a whole is the purpose of this study.

Suprageneric classifications follow those proposed by Sweet (1988), with the exception of the placement of conodonts into the phylum Chordata. This is done in accordance with more recent work that has focused on conodont hard tissue. For further discussion refer to Donoghue et al. (2000).

Phylum Chordata Bateson, 1886

Class Conodonta Pander, 1856

Subclass Conodonti Branson, 1938

Order Ozarkodinida Dzik, 1976

Family Spathognathodontidae Hass, 1959

Genus Bispathodus Müller, 1962

Type species.— Spathodus spinulicostatus E. R. Branson, 1934.

Bispathodus sp. A

Figures 3.1-3.9, 3.12, 3.16, 3.17, 3.19-3.37

Description.— P1: Carminiscaphate; Elements possess a dorsal and a ventral process, with the dorsal process being slightly shorter. When viewed from above, the element is long and straight to slightly curved. The basal cavity is small, but laterally expanded so as to be seen from above, with its maximum width being close to the ventral termination of the basal cavity. While it is typically elongated towards the dorsal end of the element, the basal cavity terminates before reaching the dorsal tip. The basal cavity is slightly asymmetric, with the caudal cup margin being less inflated, while the rostral cup margin is more laterally expanded and extends further towards the dorsal tip of the element. This asymmetry is more dramatic in juvenile specimens, although adult specimens, to a smaller degree, retain the asymmetry. The apex is positioned in the dorsal portion of the basal cavity and the terminations of lamellae can be seen within the cavity when viewed from below. Positioned above the basal cavity are one to three accessory denticles. These accessory denticles are out of line with respect to the rest of the denticles and always occur on the right side of the element. In some of the larger elements these accessory denticles have started fusing if they were positioned closely together to begin with. Denticles occur from the ventral end to dorsal tip of the element. These denticles are quite discrete in small specimens, becoming more fused as elements increase in size, with the largest elements possessing denticles that are typically fused to about half of the denticle height. The denticles

are highest at the ventral end of the process, and steadily decrease in size until the beginning of the basal cavity. The denticles directly above the basal cavity are small and all around the same size. After the termination of the basal cavity, the denticle size increases slightly, however they are not as large as the denticles located on the ventral process.

P2: Angulate; Elements are laterally compressed, possess a dorsal process and ventral process, and an enlarged cusp. The basal pit is small and does not extend much beyond the cusp.

The cusp is more than twice the size of any of the other denticles and is reclined at about a 45- degree angle. The ventral process is typically shorter than the dorsal process, deflected downward, and contains denticles that are all the same size. The dorsal process is straight, not deflected at all, and contains denticles that alternate in size between larger denticles and smaller denticles that are about half the height of the larger ones. The denticles on both processes are discrete, however the largest elements may show some web-like fusing of the denticles.

M: Digyrate; Elements possess an enlarged cusp and three processes – an adaxial process, a dorsal process, and a ventral process. The cusp is much larger than the other denticles, and while it is pointed in the adaxial direction, it twists slightly dorsally. The adaxial process is extremely abbreviated and adenticulate. The ventral process is also short, although more elongated than the adaxial process, and adenticulate. The ventral process is deflected downwards and terminates in a point. The dorsal process is elongated and deflected downward, curving slightly inward towards the distal end. The denticles on the dorsal process are small and equant.

S0: Alate; Elements possess a dramatically enlarged cusp, two lateral processes, and a caudal process. The cusp is at least twice as large as the next largest denticle. The lateral processes are elongated, deflected downward slightly, and have a distinctive curve on the aboral

margin. Due to the slight downward deflection, there is roughly a right angle between the lateral processes near the cusp, which becomes more obtuse towards the distal ends of the processes.

The denticles on the lateral processes vary in size, with a fan-like series of enlarged denticles situated near the distal end of the processes. These enlarged denticles begin directly above the start of the curve in the aboral margin and can be either directly adjacent to each other or be interspaced by smaller denticles. The enlarged denticles also tend to curve towards the cusp, although not in every case. On some of the larger specimens, the lamellae terminations can be seen on the aboral margin of the lateral processes. The caudal process is elongated, however due to breakages the total length and style of denticulation on this process cannot be determined.

S1 and S2: Bipennate; Elements possess two processes and a cusp that is not enlarged.

The processes include a caudal process and a rostral process. The caudal process is long and straight, possessing denticles that alternate in size with one to five smaller denticles separating the larger denticles. The rostral process is deflected downward slightly and has a curved aboral margin. There is a series of small equant denticles directly adjacent to the cusp on the rostral process. After this set of small denticles, there is a fan-like series of enlarged denticles at the distal end of the process.

S3 and S4: Bipennate; Elements possess two processes and an enlarged cusp. The processes include a caudal process and a rostral process. Overall, the denticles are fairly round in cross-section and discrete. The caudal process is significantly longer than the rostral process, and relatively straight. The denticles on the caudal process alternate between large and small, with one to five smaller denticles separating the larger denticles. The rostral process is smaller and deflected slightly downward and inward. The denticles on this process vary in size, and sometimes possess a fan-like series of enlarged denticles towards the distal end of the process.

Materials.— 2 P1 elements, 9 P2 elements, 10 M elements, 8 S3/S4 elements and 6 S1/S2 elements from sample 1028-18. 1 P1 element and 1 P2 element from samples 1028-19. 2 P1 elements and

1 S3/S4 element from sample 1028-20. 12 P1 elements and 4 M elements from sample 1028-21.

3 P1 elements and 1 S3/S4 element from samples 1028-22. 26 P1 elements, 29 P2 elements, 6 S0 elements, 17 M elements, 34 S3/S4 elements, and 19 S1/S2 elements from sample 1028-23. 14 P1 elements, 12 P2 elements, 4 M elements, 10 S3/S4 elements, and 4 S1/S2 elements from sample

1028-24. 35 P2 elements, 4 S0 elements 12 M elements, 48 S3/S4 elements, and 21 S1/S2 elements from sample 1028-25. 2 P1 elements, 30 P2 elements, 2 S0 elements, 5 M elements, 18

S3/S4 elements, and 35 S1/S2 elements from sample 1028-26. 1 M element from sample 1028-27.

2 P2 elements from sample 1028-28 (figure). Note that since Bispathodus sp. A and Bispathodus stabilis have identical apparatuses other than their P1 elements, the numbers reported above of non-P1 elements could correspond to either species.

Remarks.— The P1 elements found here strongly resemble older P1 elements reported to belong to the species Bispathodus aculeatus aculeatus (Ziegler et al., 1974). In addition, except for P1 morphology, the apparatus reconstruction is identical to the apparatus for Bispathodus stabilis, indicating the two apparatuses reconstructed here are very closely related and belong to the same genus. However, Bispathodus aculeatus aculeatus has not been found ranging into the Visean, with its latest recorded occurrence being lower Tournasian in age (U. duplicata conodont zone;

Klapper et al., 1975). It is possible that two different species with a similar P1 morphology

(Bispathodus aculeatus aculeatus and Bispathodus sp. A) evolved from the more morphologically conservative, long ranging Bispathodus stabilis at different times, first in the

Late Devonian (Bispathodus aculeatus aculeatus) and then in the Middle Mississippian

(Bispathodus sp. A).

Rachistognathus prolixus is a Late Visean to Serpukhovian species that has very similar

P1 elements assigned to Bispathodus sp. A here (Tynan, 1980; Baseman and Lane, 1985). This species assignment would closely agree with the age of the samples, however this identification does not explain the similarity seen between this apparatus and the apparatus for Bispathodus stabilis. Since no rachistognathid apparatuses have been described, it is difficult to interpret whether the similarity seen between the P1 elements is due to a close relationship or convergence. Apparatus reconstructions for the genus Rachistognathus would be necessary to assess if any similarity exists to the apparatus described here.

Bispathodus stabilis morphotype 2(Branson and Mehl, 1934)

Figures 3.10-3.37

1934 Spathodus stabilis Branson and Mehl, p. 188, pl. 17, fig. 20.

1974 Bispathodus stabilis; Ziegler et al., p. 103-104, pl. 1, fig. 10, pl. 3, figs. 1-3.

1992 Bispathodus stabilis; Over, p. 303, figs. 6.1-6.16, 6.21, 6.26, 6.28.

2000 Bispathodus stabilis; Capkinoglu, p. 112, pl. 4, figs. 12-16.

2003 Bispathodus stabilis; Goncuoglu et al., p. 437, pl. 1, figs. 1-2.

2005 Bispathodus stabilis; Johnston and Henderson, p. 780, figs. 5.9, 5.11, 5.40, p. 782, figs.

6.16, 6.22, 6.38, 6.49

Holotype.— Branson and Mehl, 1934, pl. 17, fig. 20. Dept. Geology, Univ. Missouri, Columbia.

C 221-4. Reillustrated by Ziegler, Sandberg and Austin (1974, pl.1, fig. 10).

Description.— P1: Carminiscaphate; When viewed from above the elements are long and straight to slightly curved, with the basal cavity being small, but laterally expanded enough as to be visible from above. The ventral edge of the basal cavity is located near the center of the element and the dorsal termination of the basal cavity occurs near but prior to the dorsal tip of the element. The basal cavity is slightly asymmetric, with the rostral cup being more elongated and positioned slightly more towards the dorsal tip of the element than the caudal cup. The apex of the basal cavity is located close to the ventral termination of the basal cavity. The denticles are discrete and remain relatively discrete throughout ontogeny. The largest denticles are located near the ventral-most portion of the element and, in some specimens, the smallest denticles are located above the basal cavity. The denticles on the dorsal process, while smaller than those near the ventral end of the element, are slightly larger than the denticles that occur above the basal cavity. However, in other specimens the denticles decrease in size from the ventral tip to the dorsal tip at a steady rate, forming a smooth transition of denticle size along the element.

Other elements: see descriptions for Bispathodus sp. A.

Materials.— 5 P1 elements, 9 P2 elements, 10 M elements, 8 S3/S4 elements and 6 S1/S2 elements from sample 1028-18. 1 P2 element from samples 1028-19. 1 S3/S4 element from sample 1028-

20. 3 P1 elements and 4 M elements from sample 1028-21. 2 P1 elements and 1 S3/S4 element from samples 1028-22. 16 P1 elements, 29 P2 elements, 6 S0 elements, 17 M elements, 34 S3/S4 elements, and 19 S1/S2 elements from sample 1028-23. 15 P1 elements, 12 P2 elements, 4 M

elements, 10 S3/S4 elements, and 4 S1/S2 elements from sample 1028-24. 23 P2 elements, 4 S0 elements 12 M elements, 48 S3/S4 elements, and 21 S1/S2 elements from sample 1028-25. 24 P1 elements, 30 P2 elements, 2 S0 elements, 5 M elements, 18 S3/S4 elements, and 35 S1/S2 elements from sample 1028-26. 1 M element from sample 1028-27. 9 P1 elements and 2 P2 elements from sample 1028-28 (figure). Note that since Bispathodus sp. A and Bispathodus stabilis have identical apparatuses other than their P1 elements, the numbers reported above of non-P1 elements could correspond to either species.

Age.— Bispathodus stabilis ranges from the lower Palmatolepis marginifera conodont zone

(middle Famennian) to the upper portion of the Gnathodus texanus zone (lower Visean).

Remarks.— The Bispathodus stabilis P1 elements described in this study conform to morphotype

2 described by Ziegler et al. (1974). Morphotype 2 elements have a basal cavity that is slightly asymmetric, and stretches to the dorsal (posterior) tip of the element, while morphotype 1 elements have a smaller basal cavity that is not as elongated or asymmetrical and terminates well before the dorsal (posterior) tip of the element. While the P1 elements described in this study have basal cavities that terminate just before the dorsal tip, they are more similar in morphology to morphotype 2 than morphotype 1.

Bispathodid apparatuses have been reconstructed and described by multiple authors from multiple localities. Over (1992) reconstructed the apparatus of Bispathodus stabilis morphotype

1 using disjunct elements recovered from the Latest Devonian to Earliest Carboniferous upper

Woodford Shale, located in Oklahoma. Johnston and Henderson (2005) described disrupted conodont bedding plane assemblages belonging to Bispathodus stabilis from the Early

Mississippian Upper Member of the Bakken Formation, located in southern Alberta and southern

Saskatchewan. Purnell and Donoghue (1998) figured a natural assemblage belonging to the genus Bispathodus found in the Upper Devonian upper Cleveland Shale, located in Cleveland,

Ohio. Sandberg and Gutschick (1984) reconstructed the apparatus of Bispathodus utahensis using disjunct elements recovered from a single limestone concretion found in the Mississippian

Delle Phosphatic Member of the Woodman Formation, located in Utah.

The P2 element for Bispathodus stabilis found by Johnston and Henderson (2005), and the P2 element for the genus Bispathodus found by Purnell and Donoghue (1998) are very similar, while the Bispathodus stabilis P2 element described by Over (1992) is slightly different.

The P2 elements belonging to Bispathodus utahensis described by Sandberg and Gutschick

(1984) is different than those described in the other bispathodid apparatuses. The Johnston and

Henderson (2005) and Purnell and Donoghue (1998) P2 element has an enlarged cusp, more fused denticles, and is longer, while the P2 element proposed by Over (1992) has more discreet denticles, a smaller cusp, and is shorter overall. The P2 described by Sandberg and Gutschick

(1984) lacks an enlarged cusp like the P2 described by Over (1992), however the element is much more elongated than Over’s P2 element, containing more denticles that are not as round in cross-section and slightly more fused. The P2 elements found in this study belonging to both

Bispathodus stabilis and Bispathodus sp. A most closely resemble the P2 elements found by

Johnston and Henderson (2005) and Purnell and Donoghue (1998) in that they have long processes and an enlarged cusp, however the denticles are not as fused.

The S0 elements found by Johnston and Henderson (2005), Purnell and Donoghue (1998), and Sandburg and Gutschick (19984) are similar. The S0 element found by Over (1992) has lateral processes that have a more acute angle between them. In this respect, the S0 elements

found in this study more closely resemble those found by Johnston and Henderson (2005),

Sandberg and Gutschick (1984), and Purnell and Donoghue (1998). However, it is difficult to determine whether the S0 elements shown by Johnston and Henderson (2005), Sandburg and

Gutschick (1984) or Purnell and Donoghue (1998) have the fan-like series of enlarged denticles on the distal ends of the lateral processes that were diagnostic in this study. In addition, the S0 elements figured by Johnston and Henderson (2005) and Sandberg and Gutschick (1984) appear to have more fused denticles than those found in this study.

The Bispathodus stabilis M elements figured by Over (1992) and Bispathodus M elements figured by Purnell and Donoghue (1998) are very similar. Both contain an enlarged cusp and a denticulate ventral process. This differs from the M element illustrated by Sandberg and Gutschick (1984) and the bispathodid M element found in this study. The bispathodid M element from the Hart River Formation is very similar to the M element of Bispathodus utahensis found by Sandberg and Gutschick (1984), both possessing short ventral processes that contain no denticles.

The Sc1 element figured by Over (1992) is very similar to the Sc1 elements figured by

Purnell and Donoghue (1998) and the Sc1 element figured by Sandberg and Gutschick (1984), all of which are nearly identical to the S3 and S4 elements recovered in this study. Similarly, the Sb1 element figured by Over (1992) and the Sb element figured by Sandberg and Gutschick (1984) are very similar to the S1 and S2 elements recovered from this study. However, the series of small equant denticles directly adjacent to the cusp on the rostral process found in elements from the Hart River Formation are not seen on the specimens figured by Over (1992) and Sandberg and Gutschick (1984). In addition, the Sb2 element figured by Over (1992) and the Sd element figured by Sandberg and Gutschick (1984) resembles some of the S elements interpreted here to

belong to Gnathodus homopunctatus, however these elements are not interpreted to be part of the

Bispathodus stabilis apparatus in this study.

These differences in gross apparatus morphology indicate that the species Bispathodus stabilis is more complex than the simple P1 element morphology would suggest. The large difference in P2 element morphology between Bispathodus stabilis morphotype 1 (Over, 1992) and Bispathodus stabilis morphotype 2 (described herein) cannot be sufficiently explained by the morphotype concept, especially in light of the P2 element similarity seen between the apparatus reconstructed in this study and those described by Purnell and Donoghue (1998) and Johnston and Henderson (2005). It is likely that the subtle differences that led to the establishment of the

Bispathodus stabilis morphotypes are not due to small variation within this species, but instead to the P1 element convergence of two different species, possibly of different genera.

Figure 3: Elements interpreted as belonging to the bispathodid apparatuses. 1-9: Bispathodus sp.

A P1 elements; 10, 11, 13-15, 18: Bispathodus stabilis P1 elements; 12, 16, 17, 19-21:

Bispathodus P2 elements; 22, 23, 27, 28: Bispathodus S0 elements; 24-26, 29-32; Bispathodus M elements; 33, 34: Bispathodus S1/2 elements; 35-37: Bispathodus S3/4 elements.

Genus Vogelgnathus Norby and Rexroad, 1985

Type species.— Spathognathodus campbelli Rexroad, 1957.

Vogelgnathus gladiolus Purnell and von Bitter 1992

Figures 5.7-5.15

1987 Vogelgnathus sp. nov.; Armstrong and Purnell, p. 107, pl. 3, figs. 16-23.

1992 Vogelgnathus gladiolus Purnell and von Bitter, p. 321, figs. 8.1-8.11.

2012 Vogelgnathus gladiolus Atakul- Özdemir et al., p. 1283 (not figured).

Holotype.— ROM 48667 (paratype, ROM 48668) from the Bogside Limestone Member,

Bewcastle Formation, Lower Border Group, Ashy Cleugh, Bewcastle, Cumbria, U.K (Purnell and von Bitter, 1992, figs 8.1-8.11).

Occurrence.— Northern Yukon Territory, Canada: Hart River Formation. Northern England:

Common Flat Limestone Member, middle Lynebank Formation to Upper Antiquatonia Member,

Cambeck Formation, Lower Border Group; Cementstone Group; Bewcastle Formation. Absent from Atlantic Canada (Purnell and von Bitter, 1992).

Description.— P1: Segminiscaphate; elements are very small in size, ranging from ~0.1 mm to

~0.2 mm in length. The length and height of the element is approximately equal. A dorsal

process is absent, and the ventral process is short, straight, and high, usually possessing four to eight denticles. The cusp, situated directly over the apex of the basal cavity, is the dorsal-most denticle and approximately the same height as the next few denticles, however denticle size decreases rapidly after that, causing the oral margin to have a convex shape. The denticles are laterally compressed and fused to about half their height. In addition, the denticles are covered with a micro-ornament that starts at the base and becomes more prominent towards the tips. The micro-ornament appears to be coarse striations, ranging in size from 1 µm to 3 µm, however when viewed at higher magnification, rather than being evenly spaced ridges that run parallel to each other, they appear to be more interwoven and uneven. In addition, some areas of the micro- ornament suggest that these ridges could possibly be hollow, however cross-sections would be needed to verify this observation. The basal cavity is conical in shape, with the outline being nearly circular when viewed from above. The basal cavity extends to the dorsal tip of the element and makes up approximately half of the element length, with the free blade accounting for the rest of the length. The bottom of the basal cavity and free blade are straight and in-line, causing the aboral margin to be straight.

S0: Alate; Elements possess an enlarged cusp, two lateral processes, and a caudal process.

The lateral processes are relatively short, with their length being approximately equal to the distance between base of the basal cavity to the tip of the cusp. The lateral processes are deflected downward, forming about a 90-degree angle between the two processes. The denticles on the lateral processes are uneven and relatively small. The caudal process is slightly longer than the lateral processes and is hooked downward at the distal end.

S: Bipennate: Elements are laterally compressed and relatively small, typically around

0.5 mm in length. The cusp is not obviously enlarged. The caudal process is significantly longer

than the rostral process and bears denticles that alternate in size, with one to four smaller denticles between each larger denticle. The rostral process is short and contains only a few denticles that are either all the same size or vary in size. The caudal process is deflected slightly downward, while the rostral process is deflected strongly downward, causing the aboral margin to have a smooth, concave outline.

Materials.— 7 P1 elements, 6 S0 elements, and 15 S elements from sample 1028-18. 1 S0 element from sample 1028-23, and 2 S0 elements from sample 1028-26.

Age.— The lower boundary of the Vogelgnathus gladiolus range is uncertain, however it has been found in the Chadian, through the Arundian, and into the Holkerian (British Dinantian stages; Purnell and von Bitter, 1992). These regional stages make up the lower half of the

Visean and correlate to below and above the lower boundary of the Gnathodus texanus conodont zone (Barham et al., 2014; Purnell and von Bitter, 1992).

Remarks.— The P1 elements recovered from the Hart River Formation greatly resemble those figured by Purnell and von Bitter (1992) from the Lower Border Group, however the elements from the Hart River Formation lack a denticulate dorsal process, while those from the Lower

Border Group have a very short dorsal process that contains a few small denticles. This difference in dorsal process denticulation may represent changes in the element through ontogeny, similar to the Hindeodus ontogeny described by Nicoll et al. (2002). As the P1 elements grow, they likely add small denticles to the dorsal process, in which case the elements recovered from the Hart River Formation would represent more juvenile specimens. In addition,

the P1 elements from the Hart River Formation have more variability in ventral process denticle size that may also correlate to ontogenetic changes as well.

The Sc elements attributed to V. gladiolus by Purnell and von Bitter (1992) are nearly identical to the S elements recovered in this study. The only difference seen is that some of the S elements from the Hart River Formation have a slightly more elongated rostral processes than the element figured by Purnell and von Bitter (1992), however this likely represents natural variability in S element morphology since other V. gladiolus S elements from the Hart River

Formation are virtually identical to the one figured by Purnell and von Bitter (1992).

There was no S0 element attributed to V. gladiolus by Purnell and von Bitter (1992), so the S0 element found in this study is a new description. None of the other elements in the apparatus were recovered from the Hart River Formation, however the M element figured by Purnell and von Bitter (1992) is similar to the M element attributed to the bispathodid species in this study.

It is possible that the M elements found in sample 1028-18 that were interpreted to be associated with the bispathodids could have belonged to the V. gladiolus specimens, however it would be very difficult for the cluster analysis to pick up such an association, especially since V. gladiolus elements are mainly found in only one sample.

Family Gnathodontidae Sweet, 1988

Genus Gnathodus Pander, 1856

Type species.— Gnathodus mosquensis Pander, 1856.

Gnathodus homopunctatus Ziegler, 1960

Figure 4

1957 Gnathodus commutatus punctatus; Bischoff, p. 24, pl. 4, figs. 7-11, fig. 14.

1960 Gnathodus homopunctatus Ziegler, p. 39, pl. 4, fig. 3.

1985 Gnathodus homopunctatus; Varker and Sevastopulo, p. 201, pl. 5.5, figs. 14, 15, 19, 21, 22.

1998 Pseudognathodus homopunctatus; Perri and Spalletta, p. 245, pl. 2, figs. 6, 7, 13.

2004 Gnathodus homopunctatus; Bermudez-Rochas et al., p. 49, pl. 7, figs. 1-6, 8-9, 11.

2005 Pseudognathodus homopunctatus; Nemyrovska, p. 45, pl. 7, figs. 2-3.

2012 Lochriea homopunctatus; Atakul-Özdemir, p. 1288, fig. 2.

2014 Pseudognathodus homopunctatus: Gatovskii and Zhokina, p. 455, pl. 1, figs. 6-11.

For further synonomy see Bermudez-Rochas et al., 2004.

Description.— P1: Carminiscaphate; The free blade and platform portion of the element are approximately equal length. The basal cavity is large, making up approximately half of the length of the element, and located at dorsal end of the element. The basal cavity starts around the centre of the element, and terminates at the dorsal tip. The apex is positioned just ventrally of the maximum width of the basal cavity. The basal cavity is symmetrical to slightly asymmetrical, with the caudal cup being slightly more inflated than the rostral cup. The upper side of the cup can either be unornamented or possess small peg-like denticles. These peg-like denticles are not as large as the denticles located on the carina, they are more circular in cross section, occur anywhere on the platform, and are never seen clustered together to form a series of denticles. The denticles of the free blade are discrete, while those located on the carina are almost entirely fused and more widely spaced. The highest denticles are located either at the

centre of the element or ventral end of the element, with denticle size decreasing away from this point. Some of the elements possess coarse striations that are visible from the base to tip of the denticles.

P2: Angulate; Elements are laterally compressed, possess a dorsal process and ventral process, and do not have an obviously enlarged cusp. The denticles on both the dorsal and ventral processes are roughly equant, however there are smaller denticles between these larger ones in some cases. In some of the specimens, striations can be seen running from the base of the denticles to the tips. The dorsal process is slightly shorter than the ventral process, and both the dorsal and ventral processes are deflected downward forming a convex oral margin and concave aboral margin.

M: Digyrate; Elements possess an enlarged cusp and three processes – an adaxial process, a dorsal process, and a ventral process. The cusp is much larger than the other denticles, and while it is pointed in the adaxial direction, it twists slightly dorsal. The adaxial process is extremely abbreviated and adenticulate. The ventral process is elongated, however it is still shorter than the dorsal process, deflected downward, and flares slightly outward towards its distal end. The ventral process is denticulate with the denticles being all approximately the same size and so small they can appear as subtle serrations along the process. The dorsal process is longer then the ventral process, and contains larger denticles that are all approximately the same size. The dorsal process is deflected downward and curves inward slightly towards the distal end.

S0: Alate; Elements possess a dramatically enlarged cusp, two lateral processes, and a caudal process. The cusp is at least twice as large as the next largest denticle. The lateral processes are long and straight to slightly curved inward towards the distal ends. The lateral

processes are strongly deflected downward, creating an acute angle between these two processes.

The denticles on the lateral processes are typically all the same height, however some small denticles can be seen in between the larger ones in some specimens. The caudal process is long and has denticles that vary in height, however more detail of the caudal process morphology is unknown due to breakages.

S1: Bipennate; Elements possess two processes and a cusp that is not enlarged. The elements include a caudal process and a rostral process. The caudal process is long and straight, possessing denticles that alternate in size with one to five smaller denticles separating the larger denticles. The caudal process is slightly twisted inward towards the distal end of the element.

The rostral process is deflected strongly inward, forming a right angle between the rostral and caudal process. The rostral process also is deflected downward at the distal end, forming a hook like structure. The denticles on the rostral process are variable in size, with the last few denticles being smaller.

S2: Bipennate; Elements possess two processes, including a caudal and rostral process, and a cusp that is not enlarged. The caudal process is long and straight, possessing denticles that alternate in size with one to five smaller denticles separating the larger denticles. The rostral process is deflected strongly inward, and the denticles are variable in size and are fanned-out and enlarged towards the distal end of the process.

S3 and S4: Bipennate; Elements possess two processes and a cusp that is either the same size as next largest denticle, or slightly larger. The processes are a caudal process and a rostral process. The caudal process is long and straight, possessing denticles that alternate in size with one to five smaller denticles separating the larger denticles. The rostral process is deflected strongly downward, so that the angle between the rostral and caudal processes is roughly a right

angle. The rostral process is also slightly twisted inward, and possesses denticles that are either all the same size, or decrease in size towards the distal end.

Materials.— 3 M elements from sample 1028-18. 1 M element from sample 1028-20. 2 P1 elements, 2 M elements and 1 S2 element from sample 1028-21. 1 M element from sample

1028-22. 2 P1 elements, 1 P2 element, 3 M elements, and 5 S2 elements from sample 1028-23. 7

M elements from sample 1028-24. 2 P1 elements, 5 P2 elements, 3 M elements, 6 S3/S4 elements,

6 S2 elements, and 4 S1 elements from sample 1028-25. 38 P1 elements, 20 P2 elements, 12 S0 elements, 59 M elements, 91 S3/S4 elements, 5 S2 elements, and 25 S1 elements from sample

1028-26. 2 P2 elements, 1 M element, and 3 S3/S4 elements from sample 1028-27.

Age.— Gnathodus homopunctatus ranges from the base of the G. texanus zone conodont zone

(lower Visean) to the lower Serpukhovian.

Remarks.— There are multiple Early Carboniferous species that have very similar P1 elements to those described here, including Vogelgnathus campbelli and Lochriea commutata. However, some of the larger elements display small poorly developed nodes on the platform that are not seen in elements belonging to V. campbelli or L. commutata. In addition, both Vogelgnathus and

Lochriea have distinctive, well-established apparatuses that do not correspond to the apparatus described here. Due to these differences, the reconstructed apparatus could not be assigned to either of these genera.

The P1 elements are similar morphologically to juvenile specimens belonging to

Gnathodus homopunctatus (Gatovskii and Zhokina, 2014; Atakul-Özdemir et al., 2012;

Nemyrovska, 2005; Bermudez-Rochas et al., 2004). In addition, there is not as much variation in size among the P1 and P2 elements when compared to the other P1 and P2 elements belonging to different species recovered from the same samples. Due to the morphology and the lack of a complete growth series, it is interpreted that this apparatus belonged to juvenile specimens of

Gnathodus homopunctatus.

The species Gnathodus homopunctatus has been assigned to many different genera including Gnathodus, Pseudognathodus, Paragnathodus, and Lochriea. The assignment of this species to either Pseudognathodus or Paragnathodus has been avoided due to reasons discussed by Atakul-Özdemir et al. (2012). The species is assigned to the genus Gnathodus over Lochriea primarily due to the morphology of the reconstructed apparatus. The apparatus, especially the P2 elements, resemble those reconstructed for various species belonging to the Gnathodus genus

(Grayson et al., 1990). In addition, the P2 and M elements described here do not correspond to those associated with the genus Lochriea, a genus that was described based on its distinctive P2 and M element morphology. This differs from the findings of Atakul-Özdemir et al. (2012), who assigned Gnathodus homopunctatus to the genus Lochriea based on the reconstruction from discrete elements they made. The apparatus figured by Atakul-Özdemir et al. (2012) is a classical Lochriea apparatus, with P2 elements that possess very discrete denticles that are more round in cross-section and M elements with an extremely enlarged cusp. This is very different from the apparatus described in this study, and these differences could not be explained by ontogenetic changes. These differences may be due to misidentification or incorrect apparatus reconstruction either in this study or by Atakul-Özdemir et al. (2012), or due to convergence of

P1 morphology. More apparatus reconstructions for Gnathodus homopunctatus should be sought in the future to resolve this issue.

Figure 4: 1-6, 9-12: Gnathodus homopunctatus P1 elements; 7, 8, 13: Gnathodus homopunctatus

S0 elements; 14, 15, 17: Gnathodus homopunctatus P2 elements, 16, 20, 21 Gnathodus homopunctatus M elements; 18, 19, 24 Gnathodus homopunctatus S1 elements; 22-23:

Gnathodus homopunctatus S2 elements; 25-27, Gnathodus homopunctatus S3/4 elements.

Gnathodus texanus Roundy, 1926

Figure 5.1-5.6

1926 Gnathodus texanus Roundy, pl. 2, fig. 8.

1979 Gnathodus texanus; Thompson, p. 230, fig. 5K.

1981 Gnathodus texanus; Ziegler, p. 139, pl. 3, figs. 5-10.

1991 Gnathodus sp. cf. G. texanus; Higgins et al., p. 251, pl. 3, fig. 1.

1998 Gnathodus texanus; Perri and Spalletta, p. 244, pl. 2, figs. 4, 5.

Holotype.— USNM 115090 from the Barnett Shale located in San Saba County, Texas (Roundy

1926, pl. 2, fig. 8).

Description.— P1: Carminiscaphate; The basal cavity is located at the dorsal end of the element, starting a little more than halfway down the element and terminating at the dorsal tip. The basal cavity is laterally expanded and strongly asymmetrical; the caudal cup is smaller and located more towards the ventral end of the element, while the rostral cup is larger and shifted towards the dorsal tip of the element. In addition, the caudal cup has a more elongated morphology, while the rostral cup is more compressed and expanded outwards. This asymmetry of the basal cavity is found in both juvenile and adult specimens, however it becomes more prominent with ontogeny. The apex is in the centre of the basal cavity, approximately in line with basal cavity’s maximum width and the terminations of lamellae can be seen within the cavity when viewed from below. There is a well-formed platform above the basal cavity, and a parapet composed of multiple fused denticles found on the caudal portion of the platform. This parapet is not pronounced in juvenile specimens and becomes more prominent with ontogeny. The denticles

that make up the parapet are approximately the same height as the denticles on the adjacent carina and are fused almost to their tips. The denticles are largest at the ventral end of the element and decrease in size towards the dorsal tip. The denticles are fused for the majority of their height, and the denticles on the platform are more widely spaced, giving these denticles a more triangular outline. The dorsal-most three to five denticles are slightly laterally expanded when viewed from above.

P2: Angulate: Elements are laterally compressed, possess a dorsal process and ventral process, and an enlarged cusp. The cusp is reclined and fused to more than half its height with the adjacent dorsal process denticle. The ventral process is deflected strongly downward and contains denticles that are all the same height. The length of the dorsal process is unknown, due to both specimens recovered being broken, however the denticle on this process are all relatively the same size and more fused than the denticles seen on the ventral process.

Materials.— 1 P1 element from sample 1028-24. 3 P1 elements and 3 P2 elements from 1028-26.

2 P1 elements from sample 1028-27.

Age.— Gnathodus texanus ranges from the base of the Gnathodus texanus conodont zone (lower

Visean) and to the top of the Gnathodus bilineatus conodont zone (upper Visean).

Remarks.— The P2 element associated with Gnathodus texanus here does not closely resemble

P2 elements that have been found to belong to other species of Gnathodus. This may be due to

Gnathodus texanus having a different P2 morphology, however due to the very low abundance of

Gnathodus texanus elements recovered the partial apparatus reconstruction made here is tenuous.

Figure 5: 1-4 Gnathodus texanus P1 elements; 5, 6: Gnathodus texanus P2 elements; 7-10

Vogelgnathus gladiolus P1 elements; 11, 12: Vogelgnathus gladiolus S elements; 13-15:

Vogelgnathus glaiolus S0 elements. All elements are to the 200 micrometer scale in the bottom right corner, except for number 7, which has its own 50 micrometer scale. This was done to show detail on the small element.

2.6 Conclusions

The Hart River Formation of the northern Yukon Territory has yielded abundant, well-preserved conodont elements that display minimal platform representation. These elements were subjected to cluster analysis to reconstruct their original apparatus composition. Partial to full apparatus reconstructions have been made for the species Bispathodus sp. A, Bispathodus stabilis morphotype 2, Gnathodus homopunctatus, Gnathodus texanus, and Vogelgnathus gladiolus. The apparatuses for Bispathodus sp. A and Bispathodus stabilis morphotype 2 were identical except the P1 element morphology, indicating a close relationship. This apparatus similarity prompted

the identification of Bispathodus sp. A, despite its similarity in P1 morphology to the Middle

Mississippian conodont species Rachistognathus prolixus.

There are some key differences in gross apparatus morphology found in this study and previous apparatus reconstructions for the same species. The Bispathodus stabilis morphotype 2 apparatus found here is more in line morphologically with the Bispathodus stabilis apparatus described by Johnston and Henderson (2005), and the Bispathodus apparatus described by

Purnell and Donoghue (1998). This differs from the Bispathodus stabilis morphotype 1 apparatus reconstructed by Over (1992), most notably in P2 element morphology. The morphologic differences seen between the Bispathodus stabilis apparatus reconstructed here and that reconstructed by Over (1992) cannot be sufficiently explained by the morphotype concept, and it is suggested that these instead represent two different species, probably of differing genera, with convergent P1 elements. This may explain why Bispathodus stabilis is such a long ranging taxon, however a more detailed study of how the Bispathodus stabilis apparatus changes through time would be necessary to test this hypothesis.

The reconstructed apparatus of Gnathodus homopunctatus also differs from previously proposed apparatus reconstructions for this species. Atakul-Özdemir et al. (2012) reconstructed the apparatus for Gnathodus homopunctatus, reassigning it to the genus Lochriea based on distinctive P2 and M elements. However, The P2 and M elements found to belong to Gnathodus homopunctatus in this study differ markedly from those described by Atakul-Özdemir et al.

(2012). The Gnathodus homopunctatus elements recovered from the Hart River Formation are interpreted as being juveniles, but the morphologic differences seen between the P2 and M elements seen here and those described by Atakul-Özdemir et al. (2012) cannot be explained by ontogenetic changes. This suggests that either the apparatus reconstruction or species

identifications made in this study or by Atakul-Özdemir et al. (2012) is flawed, or these represent different species with convergent P1 elements. The material from the Hart River

Formation is more abundant and co-occurs with few other species, indicating a stronger apparatus reconstruction than that made by Atakul-Özdemir et al. (2012). Further apparatuses for this species should be sought to determine the cause of the differences observed.

Finally, the apparatus reconstruction made for the rarely reported Vogelgnathus gladiolus agree with previous descriptions by Purnell and von Bitter (1992). The Vogelgnathus gladiolus

S0 element has been newly described here.

The overall morphologic differences observed here when compared to some previously described apparatuses for the same species suggests one of two things: there is a fundamental flaw with the apparatus reconstructions made either here or in previous studies, or the taxonomy for these species is much more complicated than P1 element morphology alone would suggest.

The agreement of the apparatuses reconstructed here and previous findings for the species

Vogelgnathus gladiolus, and to a lesser extent Bispathodus stabilis morphotype 2 indicate that apparatus reconstructions of this study are valid. This points to a greater complexity in

Mississippian conodont taxonomy that should be explored by further apparatus reconstructions.

Chapter Three: Major Contributions and Future Work

3.1 Major Contributions

In this study, a methodology for reconstructing conodont apparatuses from disjunct elements was successfully formulated and executed. Five new partial to complete apparatuses were reconstructed for Bispathodus sp. A, Bispathodus stabilis, Gnathodus homopunctatus,

Gnathodus texanus, and Vogelgnathus gladiolus. In addition, the Hart River Formation is determined to be early Visean in age, differing slightly from a previously reported late Visean to early Serpukhovian age.

The most significant contribution of this study is the reconstruction of five new conodont apparatuses. The prevalence of platform-overrepresentation, especially in Upper Paleozoic samples, makes it difficult to recognize the apparatus composition of many conodont species.

Because of this, Upper Paleozoic samples that do not show significant platform- overrepresentation, such as those from the Hart River Formation, should be used to their maximum advantage. This is especially important in light of the variations seen in the apparatus reconstructions of what are considered the same species in current taxonomy. Only by doing studies such as the one presented here will multi-element conodont taxonomy become established and understood.

The difference in apparatus structure seen here and in previous studies, especially for the species Bispathodus stabilis and Gnathodus homopunctatus, indicate greater taxonomic complexity and different evolutionary trends then have been previously proposed. The variance in Bispathodus stabilis apparatus structure seen here and in previous studies could indicate previously unidentified evolution in this long-lived taxon, however it more probably is the result of convergence of P1 morphology among different species of different genera. Similarly, the

differences seen between the apparatus of Gnathodus homopunctatus reconstructed here and the

“Lochriea” homopunctatus reconstruction of Atakul-Özdemir et al. (2012) could be explained by P1 element convergence. However, since the elements examined by Atakul-Özdemir et al.

(2012) contained abundant other co-occuring conodont species and the fact that the samples examined were turbidites (and by definition sorted), the reconstruction made by Atakul-Özdemir et al. (2012) should not be regarded as strongly as the reconstruction made here and the associations could be erroneous.

Understanding the variation seen in the entire apparatus will improve species identifications and identify instances of P1 morphology convergence. In addition, having an appreciation for the variations seen in all the elements within an apparatus will help to inform conodont workers regarding basic, but poorly understood aspects of conodont biology. Among other questions, a robust multi-element taxonomy will help researchers better understand how conodont apparatuses worked to process food, what sort of food they might have eaten, and how different conodont families are related to each other.

3.2 Future Work

There are several steps that could be taken that would improve the confidence of the conclusions drawn in this study and use the results to address further questions. These include resampling, both at the Hart River Formation and elsewhere, examining sets of elements that have already been collected, using CT scanning techniques to observe apparatus composition prior to processing, and using a morphometric approach to test the morphologic groups designated here. Finally, these results should be incorporated into the multi-element dataset developed by Donoghue et al. (2008), and modified by Atakul-Ozdemir et al. (2012). Once the

data from the newly reconstructed Hart River apparatuses is incorporated, a cladistics analysis should be run to test the evolutionary relationships of these taxa.

Resampling the Hart River Formation for conodonts would provide a check for the associations observed here. Cluster analysis should be run on the new samples, and an additional cluster analysis should be run on the new and old samples combined. This procedure could provide a test for the hypothesized element reconstructions

Areas that have previously produced apparatuses of the same species as those found here could also be resampled. This would primarily include the previously reported apparatuses compared to the Hart River apparatuses in the Systematic Paleontology portion of Chapter Two.

Sampling areas that are already known to either produce bedding plane assemblages or proportions of elements conducive to apparatus reconstruction would check the original associations reported by various authors for these areas, and provide the opportunity to directly compare the morphology of the elements to those from the Hart River Formation (rather than relying on figures).

The literature could also be searched for instances where many non-platform elements were recovered in conjuncture with the same species as those found in the Hart River Formation.

If the goal of the research was biostratigraphic in nature, the non-platform elements might not have been used to reconstruct the apparatuses, even if there were many non-platform elements found. The conodonts reported by Dover et al. (2004) are of particular interest due to the potential similarity to the samples from the Hart River Formation. Many of the conodont samples analyzed in this publication contained many of the same species as those from the Hart

River Formation, often accompanied by a large number of indeterminate ramiform and blade elements. Furthermore, the similar samples are Mississippian in age and from the Artic Alaska

terrane of northern Alaska, which is suspected to have been deposited along the passive margin of North America and subsequently rifted away with the opening of the Canada Basin (Till,

2016). Since none of the conodonts were figured, the samples of Dover et al. (2004) should be sought out and reexamined with apparatus reconstruction being the goal. Cluster analysis run on these samples would provide more information about the apparatuses of the species found in the

Hart River Formation from a similar time and place.

In addition to finding more samples, it would be advantageous to try to observe the orientation of elements from the Hart River Formation prior to processing. This could potentially be done using CT scanning. While dissolving rock quickly concentrates the conodonts, it disassociates any elements within the rock. Limestones do not typically break along bedding planes the way shales do, so observing original apparatuses within them is problematic.

It may be possible to use CT scanning to locate and observe conodont apparatuses within limestone. However, in order to get high enough resolution to see the conodonts, a small amount of rock needs to be CT scanned. This means that the location of the elements must be known to a large degree, so the rock can be cut to an appropriate size. Any new limestone samples taken from the Hart River Formation should be broken into smaller pieces and the surface of the rock should be observed for conodont elements, especially clusters of them. Then that area should be

CT scanned and cut down as necessary to get resolution high enough to see the element orientation, in hopes that it represents an original apparatus. This was attempted with the small amount of Hart River Formation rock that was left over after the majority of the rock had been dissolved for conodonts. Unfortunately, no conodonts were observed on the surface of the rock, making CT scanning unlikely to find anything. There would have been a much greater chance of

finding conodonts on the surface of the rock if this had been done with a larger amount of rock, prior to conodont processing.

CT scanning could also be used to make 3D models of the elements. Alternatively, 3D models of the elements could be created using photogrammetry, either with SEM images or microscope pictures (Eulitz and Reiss, 2015). Creating 3D models of all the elements in an apparatus would allow the modeling of the whole apparatus, and could possibly be informative as to the kinematics of the apparatus and occlusion of the elements. If models were made of different apparatuses, it could be used to better understand the functional differences of having different element morphologies. It would allow researchers to observe how morphological changes in one element affect the whole apparatus, instead of viewing the elements in isolation.

Splitting the elements into morphologically distinct groups was done purely through observation of the elements and could be tested in two different ways. First, the elements could be observed by an impartial conodont worker to see if two different people make the same groups. Alternatively, the elements could be grouped using a morphometric approach (Jones et al., 2009). Using a morphometric approach would provide a quantitative check to the qualitatively developed groups. This could be done by making measurements of the elements and running Principle Component Analysis (PCA) on those measurements. However, due to the large number of elements dealt with in this study, this would be a detailed and time-consuming task that might not necessarily produce different results.

Finally, incorporating the new apparatus reconstructions into a cladistic analysis would be a logical next step with these data. This would be important to do, since cladistic analyses rely on having complete information to produce valid results, and some of the findings of this study are different than previous findings (see the Systematic Paleontology portion of Chapter

100

Two for a discussion). To do this, character descriptions must first be assigned to the newly reconstructed apparatuses. Donoghue et al. (2008) developed a set of characters to capture the variations seen in conodont apparatuses. The next step would be to incorporate this information, along with the new apparatus reconstructions presented by Atakul-Ozdemir et al. (2012), into this multi-element dataset and run a cladistics analysis. This would hypothesize the evolutionary relationships of the species and genera recovered from the Hart River Formation.

101

References

Aldridge, R.J., Purnell, M.A., Gabbott, S.E., and Theron, J.N., 1995, The apparatus

architecture and function of Promissum pulchrum Kovacs-Endrody (Conodonta,

Upper Ordovician) and the prioniodontid plan: Philosphical Transactions of the

Royal Society B, v. 347, p. 275-291.

Armstrong, H.A., and Purnell, M.A., 1987, Dinantian conodont biostratigraphy of the

Northumberland Trough: Journal of Micropalaeontology, v. 6, p. 97-112.

Atakul-Özdemir, A., Purnell, M.A., and Riley, N.J., 2012, Cladistic tests of monophyly and

relationships of biostratigraphically significant conodonts using multielement skeletal

data – Lochriea homopunctatus and the genus Lochriea: Palaeontology, v. 55, p. 1279-

1291.

Baesemann, J.F., and Lane, H.R., 1985, Taxonomy and evolution of the genus Rachistognathus

Dunn (Conodonta: Late Mississippian to early middle Pennsylvanian): Courier

Forschungsinstitut Senckenberg, v. 74, p. 93-136.

Bamber, E. W., and Waterhouse, J. B., 1971, Carboniferous and Permian stratigraphy

and paleontology, Northern Yukon Territory, Canada: Bulletin of Canadian

Petroleum Geology, v. 19, p. 29-250.

Bamber, E. W., Henderson, C. M., Jerzykiewicz, J., Mamet, B. L., and Utting, J., 1989, A

summary of Carboniferous and Permian biostratigraphy, northern Yukon

Territory and northwest District of Mackenzie: Current Research, Part G,

Geological Survey of Canada, Paper 89-1G, p. 13-21.

102

Barham, M., Murray, J., Sevastopulo, G.D., and Williams, D.M., 2014, Conodonts of the genus

Lochriea in Ireland and the recognition of the Visean-Serpukhovian (Carboniferous)

boundary: Lethaia, v. 48, p. 151-171.

Bateson, W., 1886, The ancestry of the Chordata: Quarterly Journal of Microscopical Science, v.

26, p. 218-571.

Belka, Z., 1993, Thermal and burial history of the Cracow-Silesia region (southern

Poland) assessed by conodont CAI analysis: Tectonophysics, v. 227, p. 161-190.

Bermudez-Rochas, D.D., Sarmiento, G.N., and Rodriguez, S., 2004, Late Visean (Carboniferous)

conodonts from the Unidad de la Sierra del Castillo (Cordoba, Spain): Coloquios de

Palentologia, v. 54, p. 25-68.

Bischoff, G., 1957, Die Conodonten-Stratigraphie des rhenoherzynischen Unterkonbans mit

Berucksinchtigung der Worklumeria-Stufe und der Devon/Karbon-Grenze:

Abhandlungen Hessental Landesamtes Bodenforsch, v. 19, p. 1-65.

Branson, E.R., 1934, Conodonts from the Hannibal Formation of Missouri, Conodont Studies

No. 4: University of Missouri Studies, v. 8, p. 301-343.

Branson, E.B., 1938, Stratigraphy and paleontology of the Lower Mississippian of Missouri, Pt.

1.: University of Missouri Studies, v. 13, p. 1-208.

Branson, E.B., and Mehl, M.G., 1933, Conodont Studies: University of Missouri Studies, v. 8,

nos. 1-4, p. 349.

Branson, E.B., and Mehl, M.G., 1934, Conodonts from the Grassy Creek shale of Missouri:

University of Missouri Studies, v. 8, p. 171-259.

Bray, J.R., and Curtis, J.T., 1957, An ordination of the upland forest communities of southern

Wisconsin: Ecological Monographs, v. 27, p. 325-349.

103

Briggs, D.E.G., Clarkson, E.N.K., and Aldridge, R.J., 1983, The conodont animal: Lethaia, v. 16,

p. 1-14.

Broadhead, T.W., Driese, S.G., and Harvey, J.L., 1990, Gravitational settling of

conodont elements: Implications for paleoecologic interpretations of conodont

assemblages: Geology, v. 18, p. 850-853

Bryant, W.L., 1921, The Genesee conodonts: Bulletin of the Buffalo Society of Natural

Sciences, v. 13, no. 2, p. 1-59.

Capkinoglu S., 2000, Late Devonian (Famennian) Conodonts from Denizlikoyu, Gebze, Kocaeli,

Northwestern Turkey: Turkish Journal of Earth Sciences, v. 9, p. 91-112.

Donoghue, P.C.J., and Purnell, M.A., 1999a, Growth, function and the conodont fossil

record: Geology, v. 27, p.251-254.

Donoghue, P.C.J., and Purnell, M.A., 1999b, Mammal-like occlusion in conodonts:

Paleobiology, v. 25, p. 58-74

Donoghue, P.C.J., Forey, P.L., and Aldridge, R.J., 2000, Conodont affinity and chordate

phylogeny: Biological Reviews, v. 75, p. 191-251.

Donoghue, P.C.J., Purnell, M.A., Aldridge, R.J., and Zhang, S., 2008, The interrelationships of

‘comples’ conodonts (Vertebrata): Journal of Systematic Palaeontology, v. 6, p. 119-153,

doi:10.1017/S1477201907002234.

Dover, J.H., Tailleur, I.L., and Dumoulin, J.A., 2004, Geologic and fossil locality maps of the

west-central part of the Howard Pass Quadrangle and part of the adjacent Misheguk

Mountains Quadrangle, Western Brooks Range, Alaska: U.S. Geological Survey

Miscellaneous Field Studeis Map MF-2413, 75 p.

104

Dzik, J., 1976, Remarks on the evolution of Ordovician conodonts: Acta Palaeontologica

Polonica, v. 21, p. 395-455.

Epstein, A.G., Epstein, J.B., and Harris, L.D., 1977, Conodont Colour Alteration- an index to

organic metamorphism: U.S. Geological Survey Professional Paper 995, p. 1-27.

Eulitz, M., and Reiss, G., 2015, 3D reconstruction of SEM images by use of optical

photogrammetry software: Journal of Structural Biology, v. 191, p. 190-196.

Garzione, C.N., Patchett, P.J., Ross, G.M., and Nelson, J., 1997, Provenance of Paleozoic

sedimentary rocks in the Canadian Cordilleran miogeocline; a Nd isotopic study:

Canadian Journal of Earth Sciences, v. 34, p. 1603-1618.

Gatovskii, Y.A., and Zhokina, M.A., 2014, The ontogenesis of several late Visean conodonts

from the Verkhyaya Kardailovka Section (Southern Urals): Moscow University Geology

Bulletin, v. 69, p. 76-81.

Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M., eds., 2012, The Geological Time

Scale 2012, Volume 2: Oxford, Elsevier BV, 1144 p.

Graham, A.D., 1973, Carboniferous and Permian stratigraphy, southern Eagle Plain, Yukon

Territory, Canada in Aitken, J.D., and Glass, D.J., eds. Symposium on geology of the

Canadian Arctic: Calgary, Geological Association of Canada and Canadian Society of

Petroleum Geologists, p. 159-180.

Grayson, R.C., Merrill, G.K., and Lambert, L.L. 1990, Carboniferous Gnathodontid conodont

apparatuses: Evidence of a dual origin for Pennsylvanian taxa: Courier Forschungsinstitut

Senckenberg, v. 118, p. 353-396.

105

Goncuoglu, M.C., Boncheva, I, and Goncuoglu, Y., 2003, First discovery of middle Tournaisian

conodonts in the Griotte-type nodular pelagic limestones, Istanbul area, NW Turkey:

Rivista Italiana di Paleontologia e Stratigrafia, v. 110, no. 2, p. 431-439.

Goudemand, N., Orchard, M., Urdy, S., Bucher, H., and Tafforeau, P., 2011, Synchroton-aided

reconstruction of the conodont feeding apparatus and implications for the mouth of the

first vertebrates: PNAS, v. 108, no. 21, p. 8720-8724.

Goudemand, N., Orchards, M.J., Tafforeau, P., Urdy, S., Bruhwiler, T., Brayard, A., Glafetti, T,

and Bucher, H., 2012, Early Triassic conodont clusters from South China: Revision of the

architecture of the 15 element apparatuses of the Superfamily Gondolelloidea:

Palaeontology, v. 55, p. 1021-1034.

Hammer, O., and Harper, D.A.T., 2008, Paleontological Data Analysis: Wiley-Blackwell, 368 p.

Harris, A.G., Elleraieck, I.F., Mayfield, C.F., and Tailleur I.L., Thermal maturation values

(Conodont Color Alteration Indices) for Paleozoic and Triassic rocks, Chandler Lake, De

Long Mountains, Howard Pass, Killik River, Misheguk Mountain, and Point Hope

quadrangles, Northwest Alaska, and subsurface NPRA: U.S. Geological Survey Open

File Report 83-505, 16 p.

Hass, W.H., 1959, Conodonts from the Chappel Limestone of Texas: U.S. Geological Survey

Professional Paper 294J, p. 365-399.

Hass, W. H., 1962, Nature of Conodonts in Moore, R. C., ed., Treastis on Invertebrate

Paleontology: Lawrence, Kansas, University of Kansas Press and the Geological

Society of America, part, W: Miscellanea, p. 259

Helms, J.J., and Over, D.J., 2006, Conodont taphonomy traveling through the

alimentary canal of modern fish: Abstracts with programs – Geological Society

106

of America, v. 38, p. 4.

Higgins, A. C., and Austin, R. L., eds., 1985, A Stratigraphical Index of Conodonts: British

Micropalaeontological Society Series: Ellis Horwood Limited, Chichester, 263 p.

Higgins, A.C., Richards, B.C., and Henderson, C.M., 1991, Conodont biostratigraphy and

paleoecology of the uppermost Devonian and Carboniferous of the Western Canada

Sedimentary Basin in Orchard, M.J., and McCracken, A.D., eds., Ordovician to Triassic

Conodont Paleontology of the Canadian Cordillera: Geological Survey of Canada

Bulletin 417, p. 215-251.

Hinde, G. J., 1879, On conodonts from the Chazy and Cincinnati Group of the Cambro-

Silurian, and from the Hamilton and Genesee-Shale Divisions of the Devonian, in

Canada and the United State: Quarterly Journal of the Geological Society,

London, v. 24, p. 351-369.

Horowitz, A. S, and Rexroad, C. B., 1982, An evaluation of statistical reconstructions of

multielement conodont taxa from Middle Chesterian rocks (Carboniferous) in Southern

Indiana: Journal of Paleontology, v. 56, p. 959-969.

Jeppsson, L., 1979, Conodont element function: Lethaia, v. 12, p. 153-171.

Joachimski, M. M, Breisig, S., Buggisch, W., Talent, J.A., Mawson, R., Gereke, M., Morrow,

J.R., Day, J., and Weddige, K., 2009, Devonian climate and reef evolution: Insights from

oxygen isotopes in apatite: Earth and Planentary Science Letters, v. 284, p. 599-609.

Johnston and Henderson, 2005, Disrupted conodont bedding plane assemblages, Upper Bakken

Formation (Lower Mississippian) from the subsurface of Western Canada: Journal of

Paleontology, v. 79, p. 774-789.

107

Jones, D., Purnell, M.A., and von Bitter, P.H., 2009, Morphological criteria for recognising

homology in isolated skeletal elements; comparison of traditional and morphometric

approaches in conodonts: Palaeontology, v. 52, p. 1243-1256.

Klapper G., Lindström, M., Sweet, W. C., and Ziegler, W., 1975, Catalogue of Conodonts,

Volume II: E Schweizerbart’ sche Verlagsbuchhandlung, Stuttgart, 403 p.

Klapper G., Lindström, M., Sweet, W. C., and Ziegler, W., 1981, Catalogue of Conodonts,

Volume IV: E Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, 403 p.

Kohut, J. J., 1969, Determination, statistical analysis, and interpretation of recurrent

conodont groups in Middle and Upper Ordovician strata of the Cincinnati region

(Ohio, Kentucky, and Indiana): Journal of Paleontology, v. 43, p. 392-412.

Merrill, G.K., and Powell, R.J., 1980, Paleobiology of juvenile (nepionic?) conodonts from the

Drum Limestone (Pennsylvanian, Missourian-Kansas City Area) and its bearing on

apparatus ontogeny: Journal of Paleontology, v. 54, p. 1058-1074.

McGoff, H. J., 1991, The hydrodynamics of conodont elements: Lethaia, v. 24, p.

235-247.

McHargue, T. R., 1982, Ontogeny, phylogeny, and apparatus reconstruction of the conodont

genus Histiodella, Joins Fm., Arbuckle Mountains, Oklahoma: Journal of Paleontology,

v. 56, p. 1410-1433.

Michie, M.G., 1982, Use of the Bray-Curtis similarity measure in cluster analysis of

foraminiferal data: Mathematical Geology, v. 14, p. 661-667.

Muller, K.J., 1962, Zur systematischen Einteilung der Conodontophorida: Palaontologische

Zeitschrift, v. 36, p. 109-117.

108

Nemyrovska, T.I., 2005, Late Visean/early Serpukhovian conodont succession from the Triollo

section, Palencia (Cantabrian Mountains, Spain): Scripta Geologica, v. 129, p. 13-89.

Nicoll, R.S., 2002, New species of the conodont genus Hindeodus and the conodont

biostratigraphy of the Permian-Triassic boundary interval: Journal of Asian Earth

Sciences, v. 20, p. 609-631.

Norby, R.D., and Rexroad, C.B., 1985, Vogelgnathus, a new Mississippian conodont genus:

Department of Natural Resources Geological Survey Occasional Paper 50, 20 p.

Over, D. J., 1992, Conodonts and the Devonian-Carboniferous boundary in the Upper Woodford

Shale, Arbuckle Mountains, South-Central Oklahoma: Journal of Paleontology, v. 66, p.

293-311.

Pander, C.H., 1856, Monographie der fossilen Fische der silurischen Systems der

Russisch-Baltischen Gouvernments - Obersilurische Fische: Buchdruckerei

Kaiserlichen Akademie des Wissenschaften, p. 91.

Perri, M.C., and Spalletta, C., 1998, Conodont distribution at the Tournaisian/Visean boundary in

the Carnic Alps (Southern Alps, Italy): Palaeontologica Polonica, v. 58, p. 225-245.

Purnell, M.A., 1994, Skeletal ontogeny and feeding mechanisms in conodonts: Lethia,

v. 27, p. 129-138.

Purnell, M.A., 1995, Large eyes and vision in conodonts: Lethaia, v. 28, p. 187-188.

Purnell, M.A., and Donoghue, P.C.J., 1997, Architecture and functional morphology of

the skeletal apparatus of ozarkodinid conodonts: Philosophical Transactions of the

Royal Society of London B 352, p. 1545-1564.

Purnell, M. A., and Donoghue, P. C. J., 1998, Skeletal architecture, homologies and

taphonomy of ozarkodinid conodonts: Paleontology, v. 41, p. 51-102.

109

Purnell, M.A., and Donoghue, P.C.J., 2005, Between death and data: Biases in

interpretation of the record of conodonts: Special Papers in Paleontology:

Conodont Biology and Phylogeny: Interpreting the Fossil Record, No. 73, p. 7-26.

Purnell, M.A., and Jones, D., 2012, Quantitative analysis of conodont tooth wear and damage as

a test of ecological and functional hypotheses: Paleobiology, v. 38, n. 4, p. 605-626.

Purnell, M. A., and von Bitter, P. H., 1992, Vogelgnathus Norby and Rexroad (Conodonta): New

species from the Lower Carboniferous of Atlantic Canada and Northern England: Journal

of Paleontology, v. 66, p. 311-332.

Purnell, M. A., Donoghue, P. C. J., and Aldridge, R. J., 2000, Orientation and anatomical

notation in conodonts: Journal of Paleontology, v. 74, p. 113-122.

Rexroad, C.B., 1957, Conodonts from the Chester series in the type area of southwestern Illinois:

Report of Investigations, Illinois State Geological Survey, 43 p.

Rhodes, F.H.T., 1952, A classification of Pennsylvanian conodont assemblages: Journal of

Paleontology, v. 26, no. 6, p. 886-901.

Roundy, P.V., 1926, The micro-fauna, Part II, in Roundy, Girty, and Goldman, eds.

Mississippian formations of San Saba County, Texas: U.S. Geologcial Survey

Professional Paper 146, p. 5-17.

Sandberg, C.A., and Gutschick, R.C., 1979, Guide to conodont biostratigraphy of Upper

Devonian and Mississippian rocks along the Wasatch From and Cordilleran hingeline:

Brigham Young University Geological Studies, v. 26, p. 107-133.

Sandberg, C.A., and Gutschick, R.C., 1984, Distribution, microfauna, and source-rock potential

of Mississippian Delle Phosphatic Member of Woodman Formation and equivalents,

Utah and adjacent states, in Woodwards, J., Meissner, F.F., and Clayton, J.L., eds,

110

Hydrocarbon source rocks of the greater Rocky Mountain region: Denver, Colorado,

Rocky Mountain Association of Geologists, p. 135-178.

Schmidt, H., 1934, Conodonten-Funde in ursprunglichem Zusammenhang: Palaontologische

Zeitschrift, v. 16, p. 76-85.

Scott, H.W., 1934, The zoological relationships of the conodonts: Journal of Paleontology, v. 8,

p. 448-455.

Scott, H.W., 1942, Conodont Assemblages from the Heath Formation, Montana: Journal of

Paleontology, v. 16, p. 293-300.

Slavik, L, 2011, Lanea carlsi conodont apparatus reconstruction and its significance for

subdivision of the Lochkovian: Acta Palaeontologica Polonica, v. 56, p. 313-327.

Somerville, I.D., 2008, Biostratigraphic zonation and correlation of Mississippian rocks in

Western Europe: some case studies in the late Visean/Serpukhovian: Geological Journal,

v. 43, p. 209-240.

Sweet, W. C., 1981, Morphology and Composition of Elements: Macromorphology of elements

and apparatuses, in Robison, R. A., eds., Treatise on Invertebrate Paleontology, Part W:

Micellanea, Supplement 2: Conodonta: The Geological Society of America, Inc., Boulder

Colorado, 202 p.

Sweet, W. C., ed., 1988, The Conodonta: Morphology, Taxonomy, Paleoecology, and

Evolutionary History of a Long-Extinct Animal Phylum: Clarendon Press, Oxford, 212 p

Sweet, W. C., and Donoghue, P. C. J., 2001, Conodonts: past, present, future: Journal of

Paleontology, v. 75, p. 1174-1184.

Thompson, T.L., 1979, A gnathodont lineage of Mississippian conodonts: Lethaia, v. 12, p. 227-

234.

111

Tolmacheva, T.U., and Purnell, M.A., 2002, Apparatus composition, growth, and survivorship of

the Lower Ordovician conodont Paracordylodus gacilis Lindstrom, 1955: Palaeontology,

v. 45, p. 209-228.

Turner, S., Burrow, C. J., Shultze, H. P., Blieck, A., Reif, W. E., Rexroad, C. B., Bultynck, P.,

and Nowlan, G. S., 2010, False teeth: conodont-vertebrate phylogenetic relationships

revisited: Geodiversitas, v. 32, p. 545-594.

Tynan, M.C., 1980, Conodont biostratigraphy of the Mississippian Chainman Formation,

Western Millard County, Utah: Journal of Paleontology, v. 54, p. 1282-1309.

Varker, W.J., 1994, Multielement conodont faunas from the proposed Mid-Carboniferous

boundary stratotype locality at Stonehead Beck, Cowling, North Yorkshire, England:

Annales de la Societe geologique de Belgique, v. 116, p. 301-321.

Varker, W.J., and Sevastopulo, G.D., 1985, The Carboniferous System. Part 1 – Conodonts of

the Dinantian Subsystem from Great Britian and Ireland in Higgins, A.C., and Austin,

R.L., eds., A Stratigraphic Index of Conodonts: Chichester, The British

Micropalaeontological Society, Ellis Horwood Limited, p. 167-209.

Von Bitter, P.H., and Merrill, G.K., 1990, The reconstruction of fossil organisms using cluster

analysis: A case study from Late Paleozoic conodonts: Life Sciences Miscellaneous

Publication, Royal Ontario Museum, 23 p.

Zhuravlev, A.V., 1999, Resorption of conodont elements: Lethaia Seminar, v. 32, p. 157-158.

Ziegler, W., 1960, Die Conodonten aus den Gerollen des Zechstein Konglomerates von

Rossenray Sudwestlich Rheinberg/Niederrhein: Forschritte in der Geologie von

Rheinland und Westfalen, v. 6, p. 391-406.

112

Ziegler, W., Sandberg, C.A., and Austin, R.L., 1974, Revision of Bispathodus group

(Conodonta) in the Upper Devonian and Lower Carboniferous: Geologica et

Palaeontologica, v. 8, p. 97-112.

113