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Home , Actinoceras, Ammonoidea, Ceratitida, Endocerida, Goniatitidae, Macrocephalites

EXPERIMENT 3

MORPHOLOGICAL CHARACTERS, SYSTEMATIC POSITION AND AGE OF GENERA PERTAINING TO

Outline of Experiment______3.1 Introduction 3.5 Common Genera of Ammonoids

Expected Learning Skills 3.6 Laboratory Exercises 3.2 Requirements 3.7 Results and Discussion 3.3 Cephalopods: Systematics, General 3.8 References Morphology and Age Range 3.9 Further/Suggested Readings 3.4 Common Genera of

3.1 INTRODUCTION

In the previous experiment, you have made line drawings and described morphological characters along with palaeoecology and stratigraphic range of various genera of bivalves (pelecypods). Every of bivalves displays a set of distinctive morphological characters, on which basis they can be differentiated from each other. You know that bivalves show a wide range of adaptation, from marine to freshwater and from infaunal burrowers, epifaunal to active swimmers. Therefore, marine bivalves possess different morphological characters as compared with those of non-marine forms. In this experiment, you will work with some common genera of molluscs. They are exclusively marine and are more active, quick movers, intelligent carnivorous predators with varied shell morphology. They occupy the same ecological niche as fishes. The Class Cephalopoda consists of three subclasses: Nautiloidea, and . Among which Nautiloidea and extinct Ammonoidea are commonly found as . The third subclass, Coleoidea, comprises BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory primarily soft bodied animals. Like fishes, cephalopods are equipped with highly developed eyes and sensory organs. They are adapted to fast swimming and have developed more efficient mechanisms to locate their prey, detect predators and to escape from them. is the only living cephalopod that has an external shell. The genus Nautilus is the only survivor among the nautiloids, which is a very ancient group of cephalopods. Expected Learning Skills______After performing this experiment, you should be able to:  list the systematic positions of some common genera of nautiloids and ammonoids;  identify and describe their morphological characters;  prepare their line drawings with labeling of the morphological features; and  write their stratigraphical and palaeoecological range. 3.2 REQUIREMENTS

To perform this experiment successfully, following are the requirements:  Pen, pencil, eraser, sharpener, scale, stencil and hand lens.  Practical note-book.  Fossil specimens of nautiloids and ammoniods. 3.3 CEPHALOPODS: SYSTEMATICS, GENERAL MORPHOLOGY AND AGE RANGE 3.3.1 Systematic Palaeontology/Taxonomic Hierarchy Kingdom Animalia Subkingdom Metazoa Phylum Class Cephalopoda Subclass Nautiloidea Characteristic features: Straight, curved or coiled external shell with simple ; simple surface . Four gills are present. Example – Nautilus Age range – Late to Present Subclass Ammonoidea Characteristic features: Coiled external shell with complex surface sutures; complex surface sculpture. Gill count is unknown. It is an extinct subclass of cephalopods Example - Ammonites

36 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods Age range – Early to Late Subclass Coleoidea Characteristic features: Mostly soft bodied animals but some forms may have a straight or coiled internal shell. The organisms bear two gills. Examples – , , and extinct . Age range – to Present. 3.3.2 General Morphology of Nautiloids Nautiloids are a large and diverse group of cephalopods. They have a chambered external shell. The shell is tabular in form and may be straight, curved or spirally coiled. It is a hollow cone with two main parts – body or living chamber and (Fig. 3.1a). Each chamber is formed when an living in the body chamber grows and widens the shell, and moves forward towards the ever-growing . Each time this process leaves a space behind the body, which is repeatedly walled off by a thus forming a series of chambers (Nield and Tucker, 1985). Shell consists of a tube, which is open at the larger end and closed at the smaller end. The opening present on the larger end is termed as aperture and the tip of the smaller end is the of the shell (Fig. 3.1a). The aperture has a small notch cut on its ventral margin which is termed as hyponomic sinus (Fig. 3.1a). The shell chambers increase in size from the apex (for embryonic shells it is termed as ) towards the aperture. In the coiled forms, the inner whorls are partly or fully covered by the outer whorls (Fig. 3.1a). is a single complete turn of the shell coiling and shells may have several whorls. The space enclosed on both sides by the last whorl is described as (Fig. 3.1a). The gap between two successive whorls is termed as whorl gap. Orientation of the shell The margin of the shell towards aperture is anterior and towards the apex is posterior. The side of the shell near the mouth and hyponome is ventral and opposite side is dorsal. Dorsum is the dorsal side and venter is the ventral side of the shell. Turning to the interior or internal surface of the shell, you can see that the shell is divided into a number of chambers or camerae by transverse partitions known as septa (Fig. 3.1a). As already mentioned, the chambered portion (except last chamber) of the shell is known as phragmocone (Fig. 3.1a). In fact, phragmocone is the only part of the shell which is commonly preserved as fossil. The last chamber of the shell is described as living or body chamber. All chambers except the body chamber are filled with gas and they are also known as gas chambers. A thin calcareous tube which runs through the centre of each septum and connects all chambers is known as (Fig. 3.1a). Siphuncle is composed of septal necks and connecting rings (Fig. 3.1a). Septal necks are short funnel-like structures, which are developed around the opening in each septum. Connecting rings are the shelly tabular structures, which

37 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory connect the septal necks. The line where each septum joins the external surface of the shell is termed as suture line (Fig. 3.1b). The suture lines are either straight or slightly curved (Fig. 3.1a). The simple suture of nautiloids is also known as suture. You can see suture lines only after the removal of the shell wall or in well preserved casts of nautiloids. It is important to note that siphuncle, suture line and septal necks are important morphological features, which distinguish nautiloids from ammonoids. In nautiloids, siphuncle passes through the centre of each septum, suture line is usually simple or sometimes, it may be straight or undulating and septal neck lies on the convex side of each septum and is projected towards the apex (protoconch) of the shell. The shells of nautiloids display a variety of forms as shown in Table 3.1.

Fig. 3.1: Shell of a nautiloid: a) showing internal morphology, and b) enlarged part showing the suture lines. Table 3.1: Types of nautiolids shells. Shell name Shell form Line drawing Orthoceracone Straight conical Fig. 3.2a Cyrtoceracone Slightly curved Fig. 3.2b Gyroceracone Loosely coiled Fig. 3.2c Traphyceracone Shell having all whorls in contact Fig. 3.2d Trochoceracone Eccentric coiled Fig. 3.2e Involute nautilicone covers all other Fig. 3.2f 38 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods whorls Evolute nautilicone Earlier formed or older whorls are Fig. 3.2g all visible Exogastric Curved or straight shell with Fig. 3.2h ventral side convex (curving outside) and dorsum on the inside Endogastric Dorsal side convex (curving Fig. 3.2i outside) and venter is on the inside

Fig. 3.2: Shells of a nautiloids showing various shell forms: a) Orthoceracone, b) Cytoceracone, c) Gyroceracone, d) Traphyceracone, e) Trochoceracone, f) Involute nautilicone, g) Evolute nautilicone, h) Exogastric and i) Endogastric shell forms. Note that figures 11.3h and 11.3i are similar to figures 11.7g and 11.7h; the position of siphuncle helps us to determine whether the shell belongs to nautiloid or ammonoid. (Source: redrawn after Shrock and Twenhofel, 1987) 3.3.3 Geological History of Nautiloids The nautiloids include the oldest known cephalopods. They first appeared in the fossil record during the late Cambrian having a simple curved shell. They rapidly diversified during the and most of the groups arose during this time. Ordovician nautiloids are marked by the presence of straight or curved shells, which are much larger than the Cambrian nautiloids. The order , consisting of the living genus Nautilus, appeared in late or early Devonian times. Nautiloids began to decline during the late Palaeozoic. Most of the Palaeozoic nautiloids became extinct by the end of and only the order Nautilida having coiled shell, survived from to the present.

39 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory 3.3.4 General Morphology of Ammonoids Ammonoids are an extinct group of marine cephalopod molluscs. The morphology of ammonoids is very similar to that of nautiloids. However, ammonoids can easily be differentiated from nautiloids on the basis of location of siphuncle, suture patterns and nature of septal necks. The ammonoid shells are either tightly coiled on a single plane (i.e., ) or open helical and irregular coiled as well as straight. The planispiral coiled shells are known as homomorph ammonoids (Fig. 3.3) whereas straight, helical or irregular coiled shells are known as heteromorph ammonoids (Fig. 3.5a-c). All ammoniods had an external chambered shell, which was divisible into three parts, namely, a) protoconch, b) phragmocone and c) body or living chamber. The earliest or the first formed chamber, located in the centre of the shell, is termed protoconch (Fig. 3.3). The chambered portion of the shell is known as phragmocone (Fig. 3.3). The last and largest is termed as living or body chamber (Fig. 3.3). The opening present on the body chamber is termed aperture. The margin of the aperture is described as the peristome (Fig. 3.3). A single complete turn of the shell coiling is called a whorl and ammonoid shells may have several whorls. The hollow cone shaped space enclosed on both sides by the last whorl is described as umbilicus (Fig. 3.3). The gap between the two successive whorls is termed whorl gap.

Fig. 3.3: Shell of an ammonoid showing morphological features. In the interior or internal surface of the shell, phragmocone comprises a number of chambers or camerae (Fig. 3.3). Each chamber is marked by the successive occupation of the animal and separated by a septum (plural septa) (Fig. 3.3). A thin calcareous tube running through the ventral margin of septum that connects all chambers is known as siphuncle (Fig. 3.3). Siphuncle is composed of two parts, namely, septal necks and connecting rings (Fig. 3.3). In ammonoids, the septal necks are directed towards the aperture of the shells and connecting rings are placed towards the outer margin of the shell. The external surface of ammonoid shells show various kinds of ornamentation such as growth lines, ribs, knobs, spines, tubercles and keels. 40 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods The line where a septum joins the external surface of the shell is termed as suture line (Fig. 3.4). The suture pattern is very complex in ammonoids. It forms one of the most important characteristic features on the basis of which one can differentiate ammonoids from nautiloids. The nautiloids have a very simple suture without having any ridges (saddles) and grooves (lobes), whereas ammonoids have a complex suture pattern, in which suture line is composed of ridges and grooves (Fig. 3.4). The ridges pointing upwards (i.e., towards the aperture) are known as saddles and grooves pointing downwards (i.e., opposite direction of the saddles) are described as lobes. Three important types of sutures are recognised in the ammonoids, which are: a) Goniatitic, b) Ceratitic and c) ammonitic sutures (Fig. 3.4).

Fig. 3.4: Suture patterns in nautiloid and ammonoid cepahalopods; a) Simple suture line also known as nautiloid suture, (b-d) are complex sutures, which are commonly present in ammonoids; b) Goniatitic suture; (c) Ceratitic suture; and d) Ammonitic suture (redrawn and modified after Matthews, 1960) The ammonoid shells display a variety of forms. Some common shell forms are shown in Table 3.2. 41 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory Table 3.1: Types of ammonoids shells. Shell name Shell form Line drawing Bactriticone Straight conical Fig. 3.5a Gyroceratiticone loosely coiled Fig. 3.5b Dactylioceracone Shell having all whorls in contact Fig. 3.5c Turriliticone Eccentric coiled Fig. 3.5d Involute Body whorl covers all other whorls Fig. 3.5e ammoniticone Evolute Earlier formed or older whorls are all Fig. 3.5f ammoniticone visible Exogastric Curved or straight shell with ventral Fig. 3.5g side is convex (curve outside) and dorsum is curved on the inside Endogastric Dorsal side is convex (curved outside) Fig. 3.5h and venter is curved on the inside

Fig. 3.5: Shells of ammonoids showing various shell forms: a) Bactriticone, b) Gyroceratiticone, c) Dactylioceracone, d) Turriliticone, e) Involute ammoniticone, f) Evolute ammoniticone, g) Exogastric and h) Endogastric. (Source: redrawn after Shrock and Twenhofel, 1987) 3.3.5 Geological History of Ammonoids Ammonoids first evolved probably from the bactritid cephalopods during the early Devonian.During the early Devonian, ammonoids with goniatitic suture appeared and became nearly extinct at the end of the Permian. In the Carboniferous, the ammonoids with ceratitic suture appeared and they became common in Permian. Ammonoids with ammonite suture appeared at the close of Permian or at the start of . At the end of Cretaceous all ammonoids became extinct along with the . Their fossil record shows their global distribution. They had a short geological range (i.e. Devonian to Cretaceous), rapid rate of and are considered as excellent index fossils. 42 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods 3.4 COMMON GENERA OF NAUTILOIDS 3.4.1 Nautilus Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Order Nautilida Family Nautilidae Genus Nautilus Morphological Description: Shell is coiled planispirally. It has a chambered cone and few whorls. It bears simple septa that turned back along the siphuncle. Some Nautilus shells show complex curved septa. The suture lines that mark the traces of septa on the external surface are usually simple to wave-like (Fig. 3.6). The apex of the shell is rounded. Septal necks and connecting rings are present in the siphuncle. The septal neeks are short and pointing backward. The siphuncle is narrow and centrally located. It has a small umbilicus and simple aperture. Body chamber is larger than the chambers of the phragmocone. External surface of the shell is smooth, but may occasionally bear ribs.

(a) (b) (c) (d) Fig. 3.6: Photographs of Nautilus: a) External, b) Ventral and c) Dorsal views of a recent shell (Source: after Seuss et al., 2015) and d) External view of a fossil specimen. (Courtesy: Prof. R. Nagendra, Anna University)

Stratigraphic Range: Cambrian to Recent. Ecology: It lives in the deep ocean water and is a slow-moving scavenger or carnivorous. 3.4.2 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Nautiloidea

43 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory Order Family Genus Orthoceras Morphological Description: Shell is long, straight, slightly curved and elongate to conical in shape. Shell shows an form. Body chamber is long. The siphuncle is ventrally cylindrical and central to sub-central in position. The septal necks are simple and straight. The connecting rings are cylindrical to weakly inflatten. It has concave septa and straight suture lines. Aperture is circular in shape (Fig. 3.7). It shows varied ornamentation.

Fig. 3.7: Line drawing of Orthoceras. (Source: modified after Nield, 1987) Stratigraphic Range: Devonian to Triassic Palaeoecology: The genus was a nektonic carnivore that may have swum near the sea bed with their buoyant shell resting horizontally in the water or rested on the sea-floor. 3.4.3 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Order Family Endoceridae Genus Endoceras Morphological Description: The shell is straight like that of Orthoceras. It is cylindrico-conical to elongated in outline (Fig. 3.8). The shell is tapering towards the posterior margin. It shows an endocone (i.e., cone in cone) form. Sutures are transverse and straight. Siphuncle is very large and situated close to the ventral margin. Septal necks are very long intruding backward into the previous septum. External surface contains distinct transverse striae. 44 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods

(a)

(b) Fig. 3.8: Photographs of Endoceras. [Source: https://en.wikipedia.org/wiki/Endoceras #/media/File:Endoceras.JPG for (a) and https://upload.wikimedia.org/ Wikipedia /commons/d/d0/Endoceras.jpg for (b)] Stratigraphic Range: Ordovician Palaeoecology: The genus was an active marine predator and may have lived near the ocean floor. 3.4.4 Actinoceras Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Order Family Actinoceratidae Genus Actinoceras Morphological Description: The shell is long, cylindrical and straight (Fig. 3.9). The siphuncle is large and situated towards the ventral margin. Chambers are short. Protoconch is large. Septa are closely spaced. The septal necks are long and strongly re-curved. The connecting rings are thin and slightly inflated. Sutures are largely transverse. The shell has well developed cameral deposits.

(a) (b) Fig. 3.9: Actinoceras: a) Line drawing, and b) Photograph of a broken specimen. (Source: https://upload.wikimedia.org/wikipedia/commons/c/c4/ Actinoceras_cochleatum.jpg for b) 45 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory Stratigraphic Range: Ordovician to Silurian. Palaeoecology: Actinoceras was probably a predator of shallow to deep ocean water. 3.5 COMMON GENERA OF AMMONOIDS 3.5.1 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Family Genus Macrocephalites Morphological Description: The shell is loosely coiled and inflated. It is broad, convolute to discoidal in outline. The umbilicus is small and the shell has a constricted aperture. The shell is strongly ribbed and whorls are compressed. The whorls are more high than wide. The early whorls are highly ribbed as compared to the later ones. The body chamber is almost smooth. The external surface bears fine and dense ornamentation. Primary ribs are concave. The umbilical wall is vertical and is delimited by a sharp umbilical margin. Sutures are ammonitic and deeply impressed (Fig. 3.10).

(a) (b) (c) Fig. 3.10: Macrocephalites: (a-b) Photographs showing external and ventral views (Source: modified after Majidifard, 2018), and c) Line drawing. Stratigraphic Range: to Cretaceous Palaeoecology: It was probably a fast-moving marine offshore nektonic carnivore. 3.5.2 Otoceras Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda 46 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods Subclass Ammonoidea Order Family Otoceratidae Genus Otoceras Morphological Description: The shell is coiled, moderately involute, compressed to discoidal in outline. The umbilicus is deep, shallow to broad. The umbilical margin is rounded to distinct and rimmed. The suture is simple and ceratitic. Sometimes the suture is weakly present. Whorls are high. External surface of the shell is smooth, but some shells bear ornamentation consisting of striae and ribs. Venter margin is rounded. The umbilical wall is steep and high (Fig. 3.11).

Fig. 3.11: Line drawing of the genus Otoceras. Stratigraphic Range: Permian to . Palaeoecology: The genus Otoceras was probably a nektonic carnivore that may have lived in the shallow marine subtidal environment. 3.5.3 Ptychophylloceras Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Order Family Genus Ptychophylloceras Morphological Description: The shell involute (i.e. body whorl covers all other whorls) in shape. It has a smooth surface. The whorls are oval, flat, arched to round. The umbilicus is deep, sometimes it is narrow. Shell shows fine growth lines. Strong ridges are present on the venter. Suture lines are complex and well developed. It has thick septa (Fig. 3.12). Stratigraphic Range: Jurassic to . Palaeoecology: The genus was probably a marine shallow nektonic carnivore. 47 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory

(a) (b) Fig. 3.12: Ptychophylloceras: a) Line drawing and b) Photograph. (Source: modified after Majidifard, 2018) 3.5.4 (= Holcophylloceras) Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Order Ammonitida Family Phylloceratidae Genus Phylloceras (= Holcophylloceras) Morphological Description: The shell is smooth and involute (i.e. body whorl covers all other whorls). The whorls are high, slender and involute. Shell bears fine gentle fold and striae. The umbilicus is normally small but sometimes it may be broad and large. The umbilical wall is low and steep. It has many saddles and lobes. The saddles are simple. The external margin of the shell is rounded. The suture is complex, well preserved and consisting of shallow lobes. The ventral margin is narrow and rounded (Fig. 3.13).

(a) (b) (c) Fig. 3.13: Photograph of Phylloceras: (a-b) external view and c) Dorsal view. (Source: modified after Waagen, 1872 for b and c); (Courtesy: Prof. R. Nagendra, Anna University for a) Stratigraphic Range: Jurassic to Cretaceous. Palaeoecology: The genus was probably a marine shallow nektonic carnivore.

48 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods 3.5.5 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Order Ammonitida Family Genus Placenticeras Morphological Description: The shell is discoildal, involute and compressed. The shells of Placenticeras occur in both smaller (microconch) and larger (macroconch) forms. The umbilicus is narrow to deep. Umbilical wall is slanting. Umbilical shoulder is rounded. The external surface of the shell is weakly to strongly ornamented by ribs, spines and tubercles. The venter is smooth, narrow to slightly concave. The whorls are inflated and sometimes they are compressed to involute. It has distinct suture that consists of blunt and rounded saddles and lobes (Fig. 3.14).

(a) (b) Fig. 3.14: Photographs of Placenticeras. (Courtesy: Prof. R. Nagendra, Anna University for a); (Source: https://upload.wikimedia.org/wikipedia/ commons/ 4/40/Placenticeras_sp.%2C_ammonite_with_sea-lizard_bite_marks% 2C_Late_Cretaceous%2C_Bear_Paw_Shale_Formation%2C_Canada_- _Houston_Museum_of_Natural_Science_-_DSC01887.JPG for b) Stratigraphic Range: Late Cretaceous. Palaeoecology: The genus was probably a marine fast moving nektonic carnivore. 3.5.6 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda

49 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory Subclass Ammonoidea Order Ceratitida Family Genus Ceratites Morphological Description: The shell is flat, discoidal, planispiral and involute. The umbilicus is small, deep to wide. The external margin of the shell is convex, broad and flattened. Body chamber is short. It has a typical ceratitic suture consisting of rounded saddles and finely divided to undivided lobes (Fig. 3.15). The external lobe is short and wide. The marginal fluting is present to the septal surface. The surface near the umbilicus contains tubercles. The minor folds are present in the body whorls.

(a) (b) Fig. 3.15: Ceratites: a) Photograph (Source: modified after Waagen, 1872), and (b) Line drawing. (Source: modified after Nield and Tucker, 1985) Stratigraphic Range: Triassic. Palaeoecology: The genus was probably a marine fast moving nektonic carnivore. 3.5.7 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Order Goniatitida Family Genus Goniatites Morphological Description: The shell is highly involute, discoidal, depressed, flat, globular and fully chambered. The umbilicus is small, deep, open, but sometimes it is closed. The siphuncle is situated at the ventral margin. The whorls are wide and the external margin is rounded. It has strongly fluted septa. The septal necks are short. The connecting rings are cylindrically long. Its 50 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods suture is typically of goniatitic type consisting of rounded saddles and sharp lobes (Fig 3.16).

(a) (b) (c)

Fig. 3.16: Goniatites: (a-b) Photographs showing external and dorsal views. (Source: modified after Titus et al. 2015) and c) Line drawing of external surface (Source: redrawn after Nield, 1987)

Stratigraphic Range: Devonian to Triassic. Palaeoecology: The genus was probably a marine fast moving nektonic carnivore. 3.5.8 Systematic Palaeontology Kingdom Animalia Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Order Ammonitida Family Genus Perisphinctes

(a) (b) Fig. 3.17: Perisphinctes: a) Photograph (Source: https://commons.wikimedia.org/wiki/ File:Perisphinctes_colubrinus_-_Fossils_in_the_Arppeanum_- _DSC05518.JPG) and (b) Line drawing of the external surface.

51 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory Morphological Description: The shell is discoidal, planispiral, symmetrical and advolute. The external margin is rounded. The umbilicus is large. Umbilical wall is short. The whorls are depressed, quadrate and consist of ribs of variable size. Peristome is simple. The external surface has straight ribs. The ribs are continuous and bifurcating near the external margin of the shell. It has ammonitic suture consisting of finely divided saddles and lobes. The suture lines are thinly divided (Fig. 3.17). Stratigraphic Range: . Palaeoecology: The genus was probably a marine fast moving nektonic carnivore. 3.6 LABORATORY EXERCISES

The fossil specimens of nautiloid and ammonoid cephalopods, belonging to the genera described in Sections 3.4 and 3.5 respectively, will be provided to you for study at your study centre. You will have to perform the following activities: i) Draw the sketch of the specimen on your practical note-book. ii) Label its various morphological features (refer Figs. 3.1 and 3.5 for labeling various morphological features). iii) Write its systematic position or palaeontology. iv) Briefly, describe the morphology of the shell. v) Write the stratigraphic range and palaeoecology of the genus under study.

Format for Studying Fossil Specimens Fossil No.: …………….. Date: ……………… Systematic Palaeontology Kingdom Phylum Class Subclass Order Family Genus Systematic Palaeontology: It includes taxonomic hierarchy of the genus.

Morphological Description: It includes sketches of the specimen as well as labeling and description of its morphological features. Stratigraphic Age: It includes the age range of the genus. 3.7 RESULTS AND DISCUSSION

Based on the morphological study, the given fossil specimens have been identified as Nautilus, Orthoceras, Endoceras, Actinoceras, Otoceras,

52 Morphological Characters, Systematic Position and Experiment 3 ……………………….…………………………………………………………………………….…...... …...Age of Fossil Genera Pertaining to Cephalopods Macrocephalites, Ptychophylloceras, Phylloceras (= Holcophylloceras), Placenticeras, Ceratites, Goniatites and Perisphinctes. 3.8 REFERENCES

 Majidifard, M.R. 2018. ammonites from northeastern . Revista Brasileira de Paleontologia, 21(1):17–46.  Matthews, W.H. (1960) Texas fossils: An amateur collector’s handbook; Bureau of Economic Geology, the University of Texas, Austin, Texas  Nield, E.W. (1987) Drawing and Understanding Fossils, Pergamon Press, Oxford.  Nield, E.W. and Tucker, V.C.T. (1985) Palaeontology – An Introduction, Pergamon Press, Oxford.  Seuss B, Wisshak M, Mapes RH, Landman, NH (2015) Syn-vivo bioerosion of Nautilus by endoand epilithic foraminiferans ( and Vanuatu). PLoS ONE 10(4): e0125558. doi:10.1371/ journal.pone.0125558.  Shrock, R.R. and Twenhofel, W.H. (1987) Principles of Invertebrate Palaeontology, CBS Publishers and Distributors Pvt. Ltd., New Delhi (First Indian edition)  Titus A.L., Korn, D., Harrell, J.E., Lambert, L.L. 2015. Late Viséan (late ) ammonoids from the Barnett Shale, Sierra Diablo escarpment, Culberson County, Texas, USA. Fossil Record 18: 81–104.  Waagen, W. 1872. On the occurrence of Ammonites, associated with Ceratites and Goniatites in the Carboniferous deposits of the Salt Range. Memoir Geological survey of India 9(4): 351-358.  https://en.wikipedia.org/wiki/Endoceras#/media/File:Endoceras.JPG  https://upload.wikimedia.org/wikipedia/commons/d/d0/Endoceras.jpg  https://upload.wikimedia.org/wikipedia/commons/c/c4/Actinoceras_cochleatu m.jpg  https://upload.wikimedia.org/wikipedia/commons/4/40/Placenticeras_sp.%2C _ammonite_with_sea-lizard_bite_marks%2C_Late_Cretaceous%2C_ Bear_Paw_Shale_Formation%2C_Canada_-_Houston_Museum_of_ Natural_Science_-_DSC01887.JPG  https://commons.wikimedia.org/wiki/File:Perisphinctes_colubrinus_- _Fossils_in_the_Arppeanum_-_DSC05518.JPG 3.9 FURTHER/SUGGESTED READINGS

 Ray, A. K. (2008) Fossils in Earth Sciences, Prentice-Hall of India, New Delhi.  Shah, S.K. (2013) Elements of Palaeontology, Geological Society of India, Bangalore.  Woods, H. (2004) Palaeontology Invertebrate, (Reprinted) CBS Publishers and Distributors Pvt. Ltd., New Delhi.

53 BGYCL………………………………………………………………………………………………….…...... ….…...-138 Stratigraphy and Palaeontology: Laboratory

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