First Unequivocal Record of the Hybodont Shark Egg Capsule Palaeoxyris in the Mesozoic of North America

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First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America

Article in Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen · April 2010 DOI: 10.1127/0077-7749/2009/0028

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First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America

Jan Fischer, Freiberg, Brian J. Axsmith, Mobile, and Sidney R. Ash, Albuquerque With 7 figures and 3 tables

FISCHER, J., AXSMITH, B. J. & ASH, S. R. (2010): First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America. – N. Jb. Geol. Paläont. Abh., 255: 327–344; Stuttgart.

Abstract: The hybodont shark egg capsule Palaeoxyris humblei n. sp. is described here from four specimens collected from flood plain deposits in the Blue Mesa Member of the Chinle Formation of Late Triassic (Norian) age in Petrified Forest National Park, Arizona. This find is the first unequivocal record of Palaeoxyris in the Mesozoic of North America. The species differs from previously known taxa, especially other Triassic forms in size and banding. It also is one of the smallest species assigned to the genus. This find offers the rare opportunity of plausibly assigning these egg capsules to the hybodont nonmarine shark Lonchidion humblei as the most probable source since its disarticulated remains (teeth, fin spines) have been found at a closely adjacent locality. Originally, these eggs were deposited in special spawning grounds in the river that deposited the Newspaper Sandstone Bed. There they became attached by tendrils to a piece of drift wood or perhaps the stem or branches of a horsetail such as Neocalamites or Equisetites that grew in the shallow waters of the stream. However, the stream overflowed its banks and the egg capsules together with masses of plant debris and various invertebrates were washed onto the adjacent floodplain where they were buried and eventually fossilized.

Key words: Palaeoxyris, shark egg capsule, Hybodontoidea, Lonchidion, Norian, Late Triassic, Chinle Formation, Arizona, spawning grounds.

1. Introduction (VIALOV 1984) with a puzzling gap in the record during the Permian (SCHNEIDER & REICHEL 1989; The genus Palaeoxyris was first described by FISCHER et al. 2008b). The greatest diversity of forms BRONGNIART in 1828 from the Middle Triassic (Ani - occurs in the Late Paleozoic where they are most sian) of the Vosges, France. Since that time knowledge common in siderite concretions from the Westphalian- of the variety of shapes, the geographical distribution Stephanian (Late Pennsylvanian) of North America and the stratigraphical range of this extraordinary and Great Britain (e.g., LESQUEREUX 1870; 1880; fossil has increased greatly. Among the three morpho- KIDSTON 1886; MOYSEY 1910; LANGFORD 1958). logically similar fossil egg capsule groups Palaeo - Several Mesozoic species are known from Europe, xyris, Fayolia RENAULT &ZEILLER, 1884 and Veta - Asia and Australia (e.g., SCHMIDT 1928; CROOKALL capsula MACKIE, 1867, Palaeoxyris is the most 1930; MÜLLER 1978) and there is also a doubtful common type. It is found in brackish and freshwater record from the Late Cretaceous of Kansas, USA deposits that range from the Visean (Late Mississip - (CROOKALL 1930; BROWN 1950). pian) (SCHNEIDER et al. 2005) to the Late Cretaceous

Fig. 1. A, Stratigraphic section of the lower part of the Chinle Formation in the southern part of Petrified Forest National Park, Arizona, showing the approximate position of the locality that contained the fossils described here (Locality PFP 004) and the position of the two localities that contain the teeth attributed to the hybodont shark Lonchidion humblei (Localities PFV 122, 124). The small index map shows the location of Petrified Forest National Park east of Holbrook in east-central Arizona and the location of the study area shown in B. B, Map of the Tepees – Puerco study area in the southern part of Petrified Forest National Park, Arizona showing the localities that contained the fossils described here (Locality PFP 004) and the two localities that contain teeth attributed to L. humblei (Localities PFV 122, 124). Stratigraphic section adapted from PARKER 2006, fig. 2) and the maps are based on the Adamana 72 minute topographic quadrangle (U.S. Geological Survey, 1982) and data supplied by W. G. PARKER.

The affinities of Palaeoxyris have long been a parable to that of extant heterodont shark capsules, source of controversy (FISCHER & KOGAN 2008). As allometric properties, the absence of cuticles, and also implied by the generic name, BRONGNIART (1828) the rare co-occurrence of Palaeoxyris and skeletal considered the type species, P. regularis an inflore - remains of sharks on the same bedding plane at some scence similar to those of the extant angiosperm Xyris. localities. Consequently, Palaeoxyris is now generally Based on overall appearance and frequent occurrence accepted to be a shark egg capsule by nearly all in fossil plant assemblages, many early paleobotanists paleozoologists and paleobotanists (e.g., BROWN also regarded Palaeoxyris and the similar genera 1950; MÄGDEFRAU 1953; ZIDEK 1976; MÜLLER 1978; Fayolia and Vetacapsula as plant fossils (e.g., PRESL SCHNEIDER & REICHEL 1989; RÖSSLER & SCHNEIDER 1838; SCHIMPER & MOUGEOT 1844; ETTINGSHAUSEN 1997; SCHULTZE & SOLER-GIJÓN 2004; FISCHER & 1852; LESQUEREUX 1870; LANGFORD 1958). Further- KOGAN 2008). Although, fossil egg capsules have to more, speculations on the exact systematic position be regarded as form genera because of their am - within the plant kingdom have included nearly every biguous orthotaxonomic position (ZIDEK 1976; major vascular plant group as well as the charophy - MÜLLER 1978), they are typically treated under the cean algae (see complete reviews in CROOKALL 1932 International Rules of Zoological Nomenclature and FISCHER & KOGAN 2008). (RÖSSLER & SCHNEIDER 1997). However, other early workers (e.g., SCHENK 1867; In this contribution, the first unequivocal Palaeo - RENAULT & ZEILER 1888) noted the similarity of xyris species from the Mesozoic of North America is Palaeoxyris to the egg capsules of the living chon- described in detail from a small collection obtained drichthyan fishes. Several later studies (e.g., ZEILLER by one of the authors (SRA) from the Late Triassic 1890; MOYSEY 1910; CROOKALL 1932; MCGHEE Jr. (Norian) Blue Mesa Member of the Chinle Formation 1982; SCHNEIDER 1986; FISCHER et al. 2008a) in Petrified Forest National Park, Arizona (Fig. 1A). provided additional evidence about the affinities of This work expands on a preliminary account of this fossil. This evidence included the spiral morpho- the Chinle fossils published earlier by AXSMITH logy and parallel striae on the fossils, which are com- (2006). The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 329

2. Geological setting 2006) (Fig. 1B). The mudstone facies of the News - paper Rock Bed contains most of the well-preserved The Chinle Formation is widely exposed on the leaf and stem compressions in the park and possibly Colorado Plateau where it has a maximum thickness beyond its borders. Although plant compressions of about 400 m. It was deposited under humid to occur at other horizons, they are not as common nor as semiarid conditions (WOODY 2006) in a variety of well preserved as in this facies which contains many nonmarine environments including floodplains, palynomorphs (LITWIN et al. 1992) and approximately stream channels, lakes, small swamps, etc. Most of the 24 named plant species based on plant megafossils deposition occurred in a succession of incised paleo- such as leaves, stems, and cones. Thirteen of these valley cut and fill complexes (DUBIEL et al. 1999). As species are closely associated with the new Palaeo - a consequence, the formation consists of a number of xyris at locality PFP 004 (Fig. 1, Table 1) and several discontinuous lithologic units that have been given unidentified forms based on plant megafossils occur a variety of names since the beginning of geologic at the locality and are now under study. The mudstone research in the region in the 19th Century (see facies also contains a variety of invertebrate fossils summaries in ASH 1970 and WOODY 2006). In Petri - including the remains of conchostracans, clams, cray- fied Forest National Park and vicinity the Chinle For- fish, adult insects, and larval cases of caddis flies, mation has a thickness of about 300 m and includes although none of these are as common as the plant many of the major subdivisions recognized elsewhere fossils (MILLER & ASH 1988; AXSMITH 2006). Most of on the Colorado Plateau although the nomenclature of the logs in the Petrified Forest as well as the verte brate some of the units in the lower part has been revised fossils are found in the strata above the Newspaper recently by PARKER (2006). We follow PARKER’s Rock Bed, particularly in the upper part of the Blue recommendations in this article. Mesa Member of the Chinle Formation (PARKER The new Palaeoxyris fossils were collected from 2006). the mudstone facies of the Newspaper Rock Bed in Typically the fossils in the mudstone facies are the Blue Mesa Member of the Chinle Formation irregularly distributed and oriented, and few if any of (Fig. 1A). As defined by PARKER (2006) the News - the plant remains are preserved in growth position. paper Rock Bed consists of three distinctive facies: a Therefore, it appears that most of the fossils represent bed of brown weathering, hard, ripple-laminated, fine- organisms that inhabited either the shorelines of the grained sandstone (= Newspaper Sandstone Bed of adjacent meandering stream or lived in it and were COOLEY 1959), a bed of greenish gray, structureless, washed out onto the floodplain in a slurry of mud and highly fossiliferous mudstone (leaf-shales of STAGNER plant debris when the stream overflowed its banks 1941) which interbeds with the sandstone facies, and (AXSMITH 2006). Therefore, the occurrence of these a bed of reddish pedogenic siltstone that overlies and remains is regarded as allochthonous. interbeds with both the sandstone and mudstone Recent studies reported by FURIN et al. (2006) and facies. The sandstone and mudstone facies of the MUTTONI et al. (2004) place the Carnian-Norian Newspaper Rock Bed range from 0 to about 14 m in boundary at about 227 Ma. Therefore most if not all thickness and the siltstone facies is about 5 m thick. of the Chinle Formation is probably Norian in age, WOODY (2006) regarded the three facies as an assem - possibly middle and late Norian. This is supported by blage of genetically related floodplain deposits. new radiometric dating, which indicates that the base According to this interpretation the brown weathering of the Blue Mesa Member of the Chinle Formation sandstone represents the channel fill in a meandering has an age of about 219.2 Ma (IRMIS & MUNDIL stream system, the fine-grained mudstone facies 2008). Plant remains of the mudstone facies have been represents adjacent contemporary overbank deposits correlated to the Dinophyton zone by Ash (1980). on a distal floodplain and the overlying pedogenic silt- MILNER et al. (2006) report that the nonmarine stone consists of a series of paleosoils that developed ichthyofauna of the Blue Mesa Member belongs to the after the meandering river disappeared. nonmarine “Fish Fauna B” of Adamanian land verte- In the park, the Newspaper Rock bed is widely brate faunachrone of the southwestern United States. exposed between some distinctive small rounded hills Tetrapod fossils in the Blue Mesa Member confirm called the Tepees and the Puerco River (Fig. 1B). Most that the unit belongs to the same land vertebrate of the impression/compression plant fossils found in faunachrone (e.g., HECKERT & LUCAS 2002; PARKER the park occur here in what is informally called the 2006). “Tepees – Puerco River study area” (AXSMITH & ASH 330 J. Fischer et al.

Table 1. Estimated abundance of plant megafossils associated with the new Palaeoxyris at locality PFP 004. Abbreviations: R = rare, 1-4 specimens; C = common, 5-15 specimens; VC = very common, 16-30 specimens; EC = extremely common, > 30 specimens. Based on personal observations of one of us (SRA).

Species Abundance

Horsetails Neocalamites sp. C Equisetites bradyi EC Equesitites sp. EC Equicalastrobus chinleana R

Ferns Cynepteris lasiophora C Cynepteris bolichii R Cladophlebis daughertyi C Phlebopteris smithii VC Clathropteris walkeri VC

Bennettitaleans Zamites powellii C

Seed plants of uncertain classification Dinophyton spinosus R Pramelreuthia dubielii R Marcouia neuropteroides C

3. Terminology, morphology, and systematic issues Most of the characters and terms used in this account are based on the early investigations of Palaeoxyris and the morphologically closely related egg capsule types Fayolia and Vetacapsula by CROOKALL (1928a, 1928b, 1930, 1932) with later additions and clari - fications by ZIDEK (1976) and MÜLLER (1978). Although some terms (e.g., “pedicle”) are holdovers from the plant-based interpretation of Palaeoxyris, they are still used to assure consistent descriptive Fig. 2. Interpretative diagram of Palaeoxyris humblei terminology. Attempts at reformulating these terms by showing the principal divisions of the fossil and the typical BROWN (1950) and LANGFORD (1958) appear to have arrangement of the bands on it. The bands are designated by been counterproductive as they complicated com - Roman numerals and the segments are designated by Arabic parisons with previous species descriptions. numerals. In this diagram the course of Band I is shaded Palaeoxyris specimens have a clear three-fold (dark gray on exposed side, light grey on unexposed side) to emphasize its course around the body and onto the beak and division into a pedicle (pediculus or tail of some pedicel. Note that the rhomboidal pattern on the body of the authors), a body (corpus) and a beak (rostellum or fossil is formed by the bands where the ribs of those on the head) (Fig. 2). The body is typically fusiform in out - exposed side cross over the ribs of the bands on the un - line and composed of several spirally twisted bands exposed side of the fossil. Compare the pattern in this dia- (or ribbon-like valves) united at their margins by more gram with that in the actual specimens in Figs. 3-5 where compression during fossilization has caused imprinting of or less raised ribs or ridges. Because of the helicoidal the ribs on the unexposed side across the ribs on the exposed twisting, the bands appear repeatedly on the surface of side of the fossils. Based primarily on specimen PEFO the body forming a series of transverse rhomboids and 34350 in Fig. 3. The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 331

Fig. 3. Photograph and sketch of specimen PEFO 34350 with pedicle pointing downwards. The sketch includes all visible details on the fossil. Collarette and striations are especially noticeable on both sides in the upper part of the pedicle transition. A fragment (beak and body) of a second egg capsule is visible to the left of the more complete specimen.

linear segments (Fig. 2). The number of segments is posterior end into a long slender pedicle (Fig. 2). The higher than the number of bands but the difference beak which is nearly as long as the body, is the shorter in the number of segments and bands has been mis - end of the capsule and was used to connect the interpreted in several previous descriptions (e.g., DUN capsule to a suitable substrate. The base of the beak is 1912; ZIDEK 1976). Distinct narrow parallel striations defined by ZIDEK (1976) by a shift in rib orientation are present on both the bands and collarettes in a few from diagonal on the body to vertical on the beak (Fig. specimens. 2). The pedicle is of variable length and is typically The characteristic transverse rhomboidal pattern incomplete. It is defined by a gradual constriction to on most of the compressed specimens is merely an a narrow stalk (Fig. 2). The surface of the pedicle is accident of preservation resulting from compression also marked by ribs. Beak and pedicle have not of the spiral ribs of the bands on the exposed side of been used in the diagnosis of Palaeoxyris species in the capsule over those on the unexposed side (SCHENK previous works, while number, width, alternating 1867; QUENSTEDT 1867; SCHIMPER 1870-1872; pattern and angle of the bands have been considered as CROOKALL 1928b; ZIDEK 1976). Although the dimen- suitable specific diagnostic features among species in sions of these rhomboids have sometimes been con - the genus (MÜLLER 1978). However, the importance sidered in species diagnoses (e.g., CROOKALL 1930; of the angles in this regard is at least doubtful Müller 1978), this practice is not followed here be - (SCHNEIDER & REICHEL 1989). cause the feature is taphonomically influenced. The Many of the measurements in the description given lateral margins of the bands bear a more or less broad, below are approximate due to the gradual nature of the membranous, lateral flange-like structure termed a transitions between regions of the capsules collarette that extends outwards forming irregular, (body/beak and body/pedicle) and the small number pointed triangular appendages on the sides of com- and fragmentary condition of the specimens studied pressed specimens (Fig. 2). The body tapers gradually here. at the anterior end into a pointed beak and at the All material is housed in the collections at Petrified Forest 332 J. Fischer et al.

Holotype: PEFO 34350A, B, part and counterpart of an essentially complete egg capsule together with an associated fragment of a second egg capsule (Fig. 3).

Paratypes: PEFO 34351A, B, counterparts of egg cap sule fragment consisting of body and lower part of the pedicle (Fig. 4) and PEFO 34352A, B, counterparts of an egg capsule fragment consisting of a part of the body and a large part of the beak (Fig. 5).

Type locality: Petrified Forest National Park, locality PFP 004 (Fig. 1).

Type horizon: Mudstone facies in the Newspaper Rock Bed of the Blue Mesa Member of the Chinle Formation; Late Triassic – Norian (Zone of Dinophyton, Adamanian land mammal faunalchron).

Diagnosis: Body broadly fusiform, up to 13.0 mm long, 9.0 mm wide at the widest point, gradually tapering toward each end, traversed by seven segments of three-four heli - coidally twisted bands, bands averaging 3.0 mm in width, segments arising at an angle of 20-36º in the middle of the body, 40-50º near the ends, no alternating band pattern; beak at least 12.5 mm long, 0.75 mm wide at the most Fig. 4. Photograph and sketch of specimen PEFO 34351 distally preserved end; pedicle with gradual constriction, with pedicle pointing downwards. The sketch includes all ~ 4.6 mm wide at transition point to body, 1.4 mm wide visible details on the fossil. Collarette and striations are distally, central needle-like structure; bands lined with especially noticeable on both sides in the lower part of the collarette 1.2 mm in height, distinct fine parallel striation on pedicle transition. bands and collarettes (Table 2).

Description: The type specimen (PEFO 34350) is re - National Park, Arizona, USA where they have been cata - presented by a well-preserved part which is essentially com- loged as PEFO 34350-34352 and A and B for part and plete (Fig. 3, Table 2) and an incomplete counterpart. It has counterpart, respectively. a total length of 23.9 mm. The body is broadly fusiform in outline and is 12.7 mm long and 8.6 mm wide at its widest point near the middle of the structure and gradually and 4. Systematic paleontology evenly tapers toward each end. About 5.3 mm of the beak is preserved which represents about two-fifths of its original Genus Palaeoxyris BRONGNIART, 1828 size judging by the beak in specimen PEFO 34352 (Figs. 5-6). The pedicle is also fragmentary. It has a length of Type species: Palaeoxyris regularis BRONGNIART, 1828, 5.9 mm and a width of 4.3 mm where it is attached to the from the Middle Triassic (Anisian) of Soultz-les-Bains, body, exactly half the maximum width of the body and Northern Vosges, France. gradually tapers to a width of 0.8 mm at the edge of the rock sample. The whole specimen is traversed by six visible Diagnosis: Shark egg capsule with a clear threefold segments of three spiral bands averaging 2.9 mm in width division. Body broadly fusiform, gradually tapering toward and showing no rhythmic variation in breadth. The angle of each end, distal end gradually tapering into pointed beak, the bands changes from ~ 20° in the middle of the body, to a proximal end tapering to slender pedicel, composed of three steeper angle of ~ 30° near each end. Most conspicuous are or more helicoidally twisted bands. the remains of the 1.2 mm wide collarettes that accompany the band margins over the whole specimen and form lateral triangular appendages on one side of the body (Fig. 3). Palaeoxyris humblei n. sp. Distinctive collarettes are also present on the pedicle. Fine Figs. 2-7 striations that are parallel to the band margins are present on the surfaces of the exposed bands and collarettes. 2006 Palaeoxyris sp. – AXSMITH, p. 150-151, figs. 1-4. A poorly preserved fragment of a second egg capsule of P. humblei is exposed on the same rock surface next to the Etymology: Named after their presumed source, the type specimen (Fig. 3, Table 2). It consists of the beak and small hybodont nonmarine shark Lonchidion humblei part of the body and has a total length of 12.3 mm. The beak whose teeth and spines occur at a closely adjacent locality in is inclined toward the beak in the type specimen. Petrified Forest National Park. The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 333

its total length is unknown as in the type specimen. It is noticeable, that the central overlapping area of the bands on the pedicle appears dark and very needle-like, whereas the outer bands are barely visible. Six segments traverse the specimen, produced by four spiral bands averaging 3.1 mm in width. No alternating rhythmic pattern of the band width is observable. The angle of the bands changes from ~ 30° in the middle to a steeper angle of ~ 36° near each end of the capsule. A collarette about 1.2 mm in width is present and fine striae are visible on the exposed bands. The fourth specimen (PEFO 34352) consists of most of the beak and a part of the body of the capsule (Fig. 5, Table 2). The total length of the specimen is 23.8 mm. The body fragment is 11.3 mm long and 7.5 mm wide and is traversed by five visible segments of the original four bands. The angle of the bands varies from 40-50º. The average width of the segments is 2.9 mm. Noticeable and unique in this specimen is the nearly complete beak which has a length of 12.5 mm and a width of 0.75 mm at the most distal point. The shift in rib orientation from the body to the beak is accentuated by fine striations and is clearly visible. Collarettes are not preserved on this specimen.

Discussion: All the specimens described here represent the same type of egg capsule, and based on their size, shape, and banding characteristic are unquestionably assignable to Fig. 5. Photograph and sketch of specimen PEFO 34352 the form genus Palaeoxyris BRONGNIART, 1828. Although with beak pointing upwards. The sketch includes all visible all of the specimens are incomplete (Fig. 6), in combination details on the fossil. Striations are only clearly visible on the the features of each allow a reasonable reconstruction of the beak. entire capsule (Figs. 6-7). The body/beak length ratio in these specimens averages about 1/1, which is a common value for Palaeoxyris according to MÜLLER (1978). Only a short length of the pedicle is preserved on any of the The third specimen (PEFO 34351) is nearly as complete specimens in our collection, but in comparison to complete as the type specimen except for the beak, which is broken specimens of Palaeoxyris (e.g., CROOKALL 1930; MÜLLER off close to the body of the capsule (Fig. 4, Table 2). The 1978) a total body/pedicle length ratio up to 2 seems to total length of this specimen is 22.6 mm. The fusiform body be plausible. Furthermore, preservation in specimen PEFO is 13.3 mm long and 9.1 mm wide at its widest point. Only 34350 (Fig. 3) and especially PEFO 34351 (Fig. 4) sug- the proximal portion of the beak is preserved and has a gests a subparallel arrangement of the ribs on the pedicle length of only 2.7 mm, whereas the remnant of the pedicle is as shown in Fig. 2 similar to other Triassic forms (e.g., 4.6 mm wide at the transition point to the body and extends BRONGNIART 1828; PRESL 1838; FISCHER et al. 2007) but out 6.6 mm. The pedicle ends at the edge of the rock, so not to Paleozoic forms (FISCHER et al. 2008b). The body

Table 2. The average sizes of all three specimens of P. humblei. The width of the beak was taken at the distal end of the structure whereas the width of the pedicle was taken at the proximal end at the transition into the body. Abbreviations: t = true length; f = fragmentary length.

Specimen Figure Total Body Beak Pedicle Bands Height of Visible Numbers Length Length Width Length Width Length Width Angle Width Number Collarette Segments (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm)

PEFO 34350 3 23.9 f 12.7 t 8.6 t 5.3 f - 5.9 f 4.3 f 20°-30° 2.9 t 3 6 1.2 t PEFO 34351 4 22.6 f 13.3 t 9.1 t 2.7 f - 6.6 f 4.6 f 30°-36° 3.1 t 4 6 1.2 t PEFO 34352 5 23.8 f 11.3 f 7.5 f 12.5 f - - - 40°-50° 2.9 t 4 5 - 334 J. Fischer et al.

Fig. 6. Correlation of specimens PEFO 34350, 34351 and 34352 together with the associated fragment on 34350. A schematic reconstruction of the egg capsule type is on the far right. Noticeable is the nearly preserved natural length of the beak of PEFO 34352 in comparison to the other ones. The collarette is best preserved in PEFO 34350, whereas striations are visible on every specimen.

of the new species is traversed by three-four bands. As from the Westphalian B of Staffordshire, England. Also, previously reported by CROOKALL (1928b, 1930) and parallel striae on their bands were described and figured MÜLLER (1978) there can be a small variation in band by LESQUEREUX (1870) in P. appendiculata as well as P. numbers within one genus. Therefore, the use of the band prendeli from the Mazon Creek locality (the later specimen number by itself as a diagnostic feature among species of should be revised to P. helicteroides because of the typical the genus seems to be inadequate without using other para- alternating band widths) and by SAPORTA (1891) for P. meters. The angle of the bands varies between specimens of carbonaria. Nevertheless, the excellent preservation of the a species because of taphonomical modification. collarettes on large parts of the P. humblei specimens, The most remarkable feature of the new Chinle fossil especially in the body-pedicle transition (Fig. 3), is not compared to other species of Palaeoxyris is the presence of known in any previous records of Palaeoxyris. In fact, it an unusually well-preserved collarette in combination with strongly resembles the collarette and the striated capsule fine longitudinal striations on the bands (Figs. 2-3). The surface of modern heterodont egg capsules (see ZIDEK presence of the collarette has normally been regarded as one 1976; FISCHER et. 2008a) and supports the assignment of of the chief characters distinguishing Palaeoxyris from the these specimens of Palaeoxyris to the egg capsules of the morphologically similar egg capsule Fayolia by RENAULLT elasmobranchs. & ZEILLER (1884) and by CROOKALL (1928a), and facili - tates comparison with modern heterodont shark egg cap - Comparisons: The small size of the Chinle specimens, sules (RENAULT & ZEILLER 1888; ZEILLER 1890). Further- the smallest Palaeoxyris known up to now, and the small more, similar features have been described in certain other number of bands confine comparisons to just a select Palaeoxyris specimens. For example, LESQUEREUX (1870, number of species of Palaeoxyris (Table 3). Thus, the pos - 1880) described and illustrated noticeable pointed, trian - sible range in size variation within one species of Palaeo - gular “tooth-like” structures (= fragments of the collarette) xyris (CROOKALL 1932; MCGHEE Jr. 1982) must be con - on the body margin of P. appendiculata from the West - sidered. Among Paleozoic species P. trispiralis KIDSTON, phalian D Mazon Creek locality of Illinois, U.S.A. Such 1886 from the Westphalian B of Staffordshire, England structures were also illustrated by RENAULT & ZEILLER resembles P. humblei in having three bands, but otherwise (1888), SAPORTA (1891) and BROWN (1950). In addition, these species differ greatly since the bands are 9.0 mm wide KIDSTON (1886) illustrated similar structures in P. trispiralis in KIDSTON’s species. P. warei CROOKALL, 1928 from the The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 335

The Mesozoic species P. regularis BRONGNIART, 1828 from the Middle Triassic Voltzia sandstone of France is characterized by four bands and a body size near the range of size variation in the Chinle form but it differs slightly in the width of the bands. P. muensteri PRESL, 1838 from the Late Triassic Keupersandstein of Middle Europe is similar to P. regularis in body size. The number of bands varies up to eight according to different authors (e.g., CROOKALL 1930; MÜLLER 1978), but in specimens examined person - ally by one of us (JF) in Stuttgart only four bands were observed. Independent of this feature, P. muensteri differs in having bands up to 6.0 mm wide. It appears that the species P. muelleri FRENTZEN, 1932 from the Rhaetian of Wolfen- brunn, South Germany is most comparable to the Chinle specimens. With a body length of 22.0 mm and a body width of 11.0 mm it is closest to the size range of all known specimens of P. humbeli. Differences are in the number and width of segments, and the amount of twisting of the bands. Finally, a doubtful Palaeoxyris sp. (CROOKALL 1930) from the Late Cretaceous of Kansas shows similarities in size and band number, but the overall shape of these specimens is clearly different. All these known Mesozoic species are characterized by a parallel arrangement of ribs on the pedicle as is assumed for all the Chinle specimens. After comparison with other described material, it is apparent that the egg capsule described here mostly com - pares in all features with other Triassic species of Palaeo - xyris from Europe, such as P. regularis BRONGNIART, 1828, P. muensteri PRESL, 1838 and P. muelleri FRENTZEN, 1932. These similarities clearly demonstrate the strong relation - ship between the different Triassic Palaeoxyris species of Europe and North America. However, in spite of these similarities, the Chinle fossils differ significantly from all other published species in the whole of their characteristics, indicating that they represent a distinct and new species of Palaeoxyris defined above as P. humbeli.

5. Assignment to a probable source Fig. 7. Reconstruction of a living P. humblei egg capsule. The capsule was probably attached via a tendril from the The general assignment of Palaeoxyris and other beak to a branch or another part of a plant such as Equi - fossil egg capsule types to probable sources has setales or Neocalamites within the water. Note that the collarette is distinctly visible as a flange around the been discussed in detail by several workers (e.g., body, open in the direction of the pedicle as in living CROOKALL 1932; ZIDEK 1976; SCHNEIDER & REICHEL chon drichthyan egg capsules. Length of this idealized 1989). The greatest problem in this regard is the specimen circa 60 mm. general lack of capsules and skeletal remains of sharks preserved together on the same bedding plane or at least at the same horizon. A single rare exception Westphalian B of Swansea, England is similar in the size of was reported by SCHNEIDER (1986). Because of the the body, but differs in the number of bands with six and a absence of direct association MCGHEE Jr. (1982) com- narrower band width. P. prendeli LESQUEREUX, 1870 from the Westphalian D at the Mazon Creek locality also show pared the size distribution of fossil egg capsule types many similarities in body size and number of bands, with those of living chondrichtyhans. The almost however, the band width reaches up to 6.0 mm and the totally congruence between the allometric properties bands are weakly twisted relative to those in the Chinle spe- of chimaeroid and Palaeoxyris egg capsules was used cimens. The poorly described P. intermedia LESQUEREUX, as evidence that Palaeoxyris was possibly an ancient 1880 from the Westphalian of Pennsylvania seems to be similar in body size and width of bands, but no more data group of egg capsules with holocephalian affinity, a are available. Furthermore, all those Paleozoic species are view which was first suggested by MOYSEY (1910) characterized by twisted ribbing on the pedicle. and critically discussed by ZIDEK (1976). 336 J. Fischer et al.

Table 3. Comparisons of the sizes and the number and widths of the bands of P. humblei n. sp. in all suitable species and records of Palaeoxyris.

Taxon & author Body Bands Age Locality References Length Width Number Width (mm) (mm) (mm)

P. humblei Late Triassic Petrified Forest National AXSMITH 2006, this paper 12 8 3-4 2.9-3.1 Norian Park, Arizona, USA this paper

P. intermedia 25-35 7-17 2 Late Carboniferous Pennsylvania, USA KIDSTON 1886; LESQUEREUX1880 Westphalian ZEILLER 1890

P. trispiralis 40-90 20-35 3 9 Late Carboniferous Staffordshire, Digby, CROOKALL 1928b, 1930, KIDSTON 1886 Westphalian B Shipley, England 1932; MÜLLER 1978

P. warei 18 7 6 1.5-1.8 Late Carboniferous Swansea, Ystragynlais MÜLLER 1978 CROOKALL 1928b Westphalian B South Wales, England

P. prendeli 25-34 12-18 4 2.5-6 Late Carboniferous Mazon Creek, Illinois, LESQUEREUX 1880; LESQUEREUX Westphalian USA; England; France, KIDSTON 1886; 1870 MOYSEY 1910; CROOKALL 1928b, 1930, 1932; LANGFORD 1958; MÜLLER 1978

P. regularis 35-40 12-25 4 5 Middle Triassic Sultz-les-Basin, PRESL 1838; SCHIMPER BRONGNIART Anisian Northern Vosges, & MOUGEOT 1844; 1828 France SCHMIDT 1928; CROOKALL 1930, LANGFORD 1958; GALL 1971; MÜLLER 1978

P. muensteri 38-89 10-30 4-8 3-6 Late Triassic Bamberg, Bayreuth, SCHIMPER & PRESL Rhaetian Tübingen, Germany; MOUGEOT 1844; 1838 Scandinavia SCHENK 1867; SAPORTA 1891; SCHMIDT 1928; CROOKALL 1930, FRENTZEN 1932; LANGFORD 1958; MÜLLER 1978

P. muelleri 22 11 3 6 Late Triassic Wolfenbrunn, Swabia FRENTZEN 1932 FRENTZEN 1932 Rhaetian Germany

P. sp. 28 14 3 3-5 Late Cretaceous Ellsworth County, BROWN 1950; CROOKALL 1930 Kansas, USA MÜLLER 1978

Another indirect method of determining their hybodonts and ctenacanths. The stratigraphical range source is to compare the stratigraphical distribution of Palaeoxyris (Carboniferous to Cretaceous) is of egg capsule types and chondrichthyan groups. much greater than that of Fayolia or Vetacapsula Because of the occurrence of these remains in (CROOKALL 1930; ZIDEK 1976; MÜLLER 1978). Thus brackish and nonmarine deposits, the possible groups far, only the hybodont sharks are known to have a of chondrichthyans are restricted to the xenacanths, comparable geological range in marine and nonmarine The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 337 sediments (e.g., ZANGERL 1981; CAPPETTA 1987). The are missing from the lower part of the Chinle For - theory that the hybodont sharks were the most likely mation (MURRY & KIRBY 2002). “Acrodus” is only source of Palaeoxyris capsule types was first plausib- known from a questionably identified tooth from ly argued by CROOKALL (1932), subsequently discus- the Placerias Quarry, whereas all other specimens sed by ZIDEK (1976) and MÜLLER (1978), and finally referred to Acrodus from the Chinle Formation by confirmed by SCHNEIDER (1986) and SCHNEIDER & MURRY (1989) were newly assigned to Reticulodus by REICHEL (1989). SCHNEIDER (1986) described packs MURRY & KIRBY (2002). Furthermore, Diplolonchi - of P. helicteroides together with remains of the dion is restricted to the upper Kalgary site in the small hybodont nonmarine shark Lissodus lacustris Tecovas Formation, Texas. Its limited occurrence may GEBHARDT, 1988 within the same bed in the Late point to an endemic species. Carboniferous Wettin Subformation in the Saale Lonchidion humblei MURRY, 1981, the most com- Basin, Germany. Moreover, FISCHER et al (2007) mon hybodont taxon in the Chinle Formation, is described a new occurrence of Palaeoxyris in the known from several different localities in Arizona, Late Triassic Madygen Formation of Kyrgyzstan Texas and New Mexico (HECKERT 2004; HECKERT et suggesting that small hybodont freshwater sharks al. 2007). Since most finds are from the Norian occurred in these nonmarine strata. Proof followed in (Otischalkian and Adamanian), it appears that the 2008 when the first small Lissodus-like hybodont stratigraphic range of this genus includes the entire tooth was discovered at an adjacent locality by one of Late Triassic in western North America (HECKERT us (JF). Furthermore, SCHNEIDER & REICHEL (1989) 2004; HECKERT & LUCAS 2006). According to MURRY were able to elaborate and substantiate the assignment (1989) and HUBER et al. (1993), localities in the Blue of Fayolia egg capsules to diploselachid sharks as had Mesa Member in Arizona that contain L. humblei been proposed much earlier by RENAULT & ZEILLER include the Placerias-Downs quarries in Apache (1888) and ZEILLER (1890). County and in the so-called Dying Grounds (Locality Several different sharks are known from the Chinle PVP 122) and Crocodile Hill (Locality PVP 124) Formation which could be the source of P. humblei. localities within Petrified Forest National Park (Fig. Of these, the most abundant chondrichthyan is “Xena- 1A-B) where they occur only about 15 m above and canthus” moorei WOODWARD, 1889 (= Triodus moorei 1500 m southeast of the egg case locality (Locality according to HECKERT & LUCAS 2006), which numer - PFP 004). At these localities L. humblei is only known ically dominates the shark assemblage (HECKERT from numerous isolated teeth and ridged fin spine 2004). However, this species is remarkably small in fragments (MURRY 1981). Comparing the size of these contrast to Paleozoic xenacanth species like Xena - teeth to the tooth size/body length ratio of articulated canthus or Orthacanthus, probably as result of an skeletons of the closely related genus Lissodus endemic evolution in the Late Triassic. Within the (BROUGH 1935; ANTUNES et al. 1990), a length of Chinle Formation, its remains are restricted to strata of twenty to thirty centimeters for L. humblei seems Otischalkian and primary Adamanian age (HUBER et plausible. The overall shape of the small teeth is al. 1993; HECKERT & LUCAS 2006). According to characteristic of a crushing type heterodontous SCHNEIDER & REICHEL (1989) xenacanth egg capsules dentition (HECKERT et al. 2007) of a durophagous are the Fayolia type; therefore, this species is probab- bottom-dwelling shark (DUFFIN 1985). ly not the source of P. humblei. It is important to recognize that there is a close The most common non-xenacanth sharks in the morphological relationship between remains of Lon- Chinle Formation are the hybodonts “Acrodus” sp. chidion and Lissodus, which is why DUFFIN (1985) TANNENBAUM KAYE & PADIAN, 1994, Reticulodus synonymized the two genera. However, this action was synergus MURRY & KIRBY, 2002, Diplolonchidion later reversed by REES & UNDERWOOD (2002), who murryi HECKERT, 2004, and Lonchidion humblei preferred the retention of Lonchidion as a valid genus MURRY, 1981. Due to the assignment of Palaeoxyris together with Lissodus in the family Lonchidiidae. to hybodont sharks as discussed above, the putative Recently, REES (2008) published preliminary results source of P. humblei is most likely among these about the interrelationship of Mesozoic hybodont species. Whereas remains of “Acrodus”, Diplolonchi- sharks in which he separated Lissodus from the dion and Lonchidion occur at the same stratigraphic Lonchidiidae but did not assign it to another family. level (Adamanian) as P. humblei (MILNER et al. 2006), Hence the whole phylogeny of Lissodus is still the remains of the generally widespread Reticulodus under discussion (see review in FISCHER 2008) be- 338 J. Fischer et al. cause identifying hybodont genera based on isolated or deposited under rocks or in crevices. After ovi - elements is so problematic (DUFFIN 1985; DUNCAN position, no further parental care is provided. Thus, 2004; HECKERT 2004). A detailed discussion of this the horny egg capsule protects the embryo throughout problem is far beyond the scope of this paper. For us, development against predators, but does not restrict only the revision by REES & UNDERWOOD (2002) of the movement of ions, ammonia, urea as well as other Mesozoic species has been convincingly applied, larger organic molecules through the capsule wall regarding Lonchidion and Lissodus as close related (KORMANIK 1992; 1993; POWTER & GLADSTONE members of the same family. 2008a). Egg capsules of sharks are preyed on by Lissodus lacustris is considered to be the source of numerous organisms, e.g., gastropods, teleosts and P. helicteroides based on the convincing association other sharks, so their mortality rate is extremely high documented by SCHNEIDER (1986). It seems to be (COX & KOOB 1993; CARRIER et al. 2004; POWTER & obvious that a closely related shark of the same GLADSTONE 2008a). A few weeks after deposition, family, of a similar size and the same ecological niche small slits open in the capsule (pre-hatching) allowing was the logical source of the Palaeoxyris egg capsules. direct water circulation around the embryo Thus, the presence of many teeth attributed to L. (LECHENAUALT et al. 1993). These slits are sealed in humblei by HECKERT (2004) and HECKERT et al. freshly deposited capsules by a mucous plug, which (2007) in closely adjacent parts of the Blue Mesa dissolves slowly and is fully gone in several weeks Member of the Chinle Formation strongly suggests (RODDA & SEYMOUR 2008). The whole incubation that this shark was the source of P. humblei. period of the eggs may last a few months to more than one year (COMPAGNO 1990; CARRIER et al. 2004). Hatchlings are fully developed miniatures of the adult, 6. Paleoecological implications and hence precocial. Moreover, COMPAGNO (1990) Little is known about the behavior of fossil sharks notes habitat selection behavior for the young of some because their cartilaginous skeletons are rarely pre - species that helps them avoid conspecific predators as served in the fossil record. Normally the mineralized well as other predatory sharks. teeth, spines and scales are the only parts of these Because of the similarities of P. humblei n. sp. to fish to be fossilized, and many chondrichthyan genera extant heterodont egg capsules it seems plausible that are known only from such isolated remains (e.g., the fossil also had a similar collagen-like composition ZANGERL 1981; CAPPETTA 1987). Thus, conclusions that provided mechanical protection and acted as a about their feeding behavior are drawn mainly from barrier to environmental pathogens for the embryo comparisons of the teeth and scales of fossil and throughout its development. Although pre-hatching extant elasmobranchs. Egg capsules, such as those structures or slits are described in other examples of described here afford an additional opportunity to Palaeoxyris (ZIDEK 1976; MÜLLER 1978) they have expand knowledge about the reproductive behavior of not been observed in the current specimens of P. ancient sharks and to compare their egg capsules with humblei. Nothing can be said about the length of the those of modern chondrichthyans. incubation period in our material but because non - All extant chondrichthyans have internal fertili - marine habitats tend to be less stable than marine zation (COMPAGNO 1990; HAMLETT & KOOB 1999; equivalents (COMPAGNO & COOK 1995) it is doubtful CARRIER et al. 2004; POWTER & GLADSTONE 2008b). that it lasted more than one year. 43 % of all modern elasmobranchs are oviparous The function of the collarettes is not completely according to COMPAGNO (1990), laying eggs encased understood in either fossil or extant egg capsules. in a tough, horny, yet flexible capsule composed of However, COMPAGNO (1990) reports that at least one cross layers of collagen fibres or collagen-like species of heterodont shark picks up the capsule with material (KORMANIK 1993; RODDA & SEYMOUR its mouth after oviposition and wedges it like a screw 2008). Egg capsules may be laid daily or weekly, with the pointed end in a rock or coral crevice. and often in pairs (COMPAGNO et al. 2005). There is Although this would explain the screw-like shape evidence that females spawn in localized nursery or of the egg capsules in modern bullhead sharks, the spawning grounds (COX & KOOB 1993; HAMLETT & process is probably restricted to egg types without KOOB 1999; COMPAGNO et al. 2005). Their egg tendrils. Since evidence of tendrils that unequivocally capsules are anchored by coiled tendrils onto bottom served as anchoring devices is proved in Palaeoxyris structures like seaweed, drift wood, living plants, etc., and in Fayolia this assumption does not necessarily The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 339 apply to these two genera. An explanation for water migration behavior for female nonmarine sharks circulation alongside the surface to the pre-hatching during the Carboniferous to particular spawning slits is also imaginable for these structures, but not grounds more or less far from their normal habitat to proven. Therefore, a satisfying answer is not currently protected areas with mangrove-like stands of Cala - possible and can only be reached through further mites or the like. Such seasonal migration appears studies on extant egg capsules. An example of such a to be an ancient specific phylogenetic pattern of study is currently being conducted by J. CARUSO behavior of oviparous female nonmarine sharks, such from the Melbourne Aquarium who is looking at the as that found in modern oviparous sharks of the con - form and function of the flanges on the egg capsules tinental shelf (SCHNEIDER & REICHEL 1989). This may of Heterodontus portusjacksoni (CARUSO, personal also explain why the skeletal remains of nonmarine communication). sharks and their egg capsules are rarely found at the The fact that the P. humblei specimens described same localities in Triassic strata. here were found closely associated in a very small Whereas all Palaeoxyris have been found in area (~10 cm x 5 cm x 2 cm) argues for a cluster of brackish or freshwater strata so far, no extant ovi - several attached individuals. Clusters of two or more parous elasmobranchs are known to deposit their Palaeoxyris capsules have been described, for P. egg capsules in freshwater environments (DULVY & jugleri by ETTINGSHAUSEN (1852), for P. muensteri REYNOLDS 1997; SCHULTZE & SOLER-GIJÓN 2004). and P. muelleri by FRENTZEN (1932), and for P. Therefore, SCHULTZE & SOLER-GIJÓN (2004) sup - helicteroides by SCHNEIDER (1986). CROOKALL posed that the reproductive strategy of these fossil (1932) clearly demonstrated that the attachment of elasmobranchs is an explicit marine signal, but for Palaeoxyris was by their beaks, or more likely, by KOHRING (1995) their distribution pattern indicates coiled tendrils extending from the beak-end of the that the development of horny egg capsules is directly capsule (Fig. 7). This is supported by finds of Palaeo - correlated with the colonization of Palaeozoic fresh - xyris from the Mazon Creek locality attached to wood water environments by some groups of chondrich - fragments by a tendril connected to the beak (LANG- thyans. The colonization could be caused to free those FORD 1958), or by two Palaeoxyris from the German elasmobranchs from competition with more advanced Saar Basin that were found attached to each other by marine sharks in similar niches (e.g. GRAY 1988) or long twisted tendrils that came from their beaks palaeogeographical procceses, which separated dia- (WATERLOT 1934). P. humblei also seems to confirm drome populations from the marine habitat (RÖSSLER this. The beak of PEFO 34350 and the beak of the & SCHNEIDER 1997). According to KOHRING (1995) associated capsule fragment on the same rock surface modern oviparous chondrichthyans retained the are pointed in the same direction to what could have development of stable egg capsules from their, at least been a common point of attachment, suggesting they partial, freshwater ancestors. With the extinction of were originally agglutinated by their beaks (Fig. 3). At the hybodonts in the marine as well as freshwater that time the egg capsules were probably attached environments at the end of the Mesozoic and no singly (Fig. 7), or in pairs, or clusters of more recolonization of nonmarine environments by modern specimens to driftwood or plants rooted on the floor in oviparous groups, chondrichthyan egg capsules the shallow waters of the stream that deposited the vanished from the continental realm. Newspaper Sandstone Bed. Then during a period of high water they were washed out of their spawning 7. Conclusions ground together with associated plant debris (Table 1) and invertebrates and deposited allochthonously in Four fragmentary specimens of a cone-like structure muddy sediment on the adjacent floodplain. were found in the Late Triassic (Norian) mudstones of A plausible explanation for the general absence of the Newspaper Rock bed of the Blue Mesa Member in nonmarine shark remains and their egg capsules at Petrified Forest National Park, Arizona. Because of the same localities in the fossil record is that it is their distinctive body, pedicle and beaks, these fossils primarily the result of behavioral and paleobiological are assigned to Palaeoxyris BRONGNIART, 1828, a non- effects. For example, based on distinct biotope pre - marine type of chondrichthyan egg capsule. In spite of ference for deposition of egg capsules and the general great similarities to other known species of Palaeo - habitat of adult sharks SCHNEIDER & REICHEL (1989) xyris, especially those from the Triassic of Central and RÖSSLER & SCHNEIDER (1997) suggest a seasonal Europe, such as P. regularis BRONGNIART, 1828, P. 340 J. Fischer et al. muensteri PRESL, 1838 and P. muelleri FRENTZEN, tribution will raise awareness of the presence of these 1932, the new find represents a new species which we fossils in the Chinle Formation as well as in similar here name P. humblei n. sp., since it has such a unique alluvial deposits. Perhaps, having been alerted by combination of features. This find is the first record of this work, future discoveries of Palaeoxyris in the Palaeoxyris in the Chinle Formation, and, further - Chinle Formation will provide additional information more, the first unequivocal record of the fossil in the about the paleoecology of these egg capsules, on Mesozoic of North America. Although there are habitat constraints and migration patterns of the chon- enough differences to warrant placing the Chinle drichthyan fauna, and on the nonmarine ecosystems of material in a new species, the similarities demonstrate the Late Triassic as well. a strong relationship between the different Triassic Palaeoxyris taxa of Europe and North America. It is also unique in being the smallest of this kind of Acknowledgements egg capsule. Most noticeable on the new fossils are the unusually well-preserved collarettes together with We gratefully acknowledge the assistance of Dr. R. BÖTTCHER (Staatliches Museum für Naturkunde Stuttgart) parallel striations. In comparison to living heterodont for providing JF with crucial Triassic egg capsules for study shark egg capsules, which show a well-developed and comparisons. M. BUCHWITZ, S. VOIGT and O. BÉTHOUX collarette and a striated surface, both characteristic (Freiberg) made very helpful comments about the article features of P. humblei, support the theory that and useful corrections. I. KOGAN (Freiberg) translated Palaeoxyris is the egg capsule of ancient sharks. several essential French publications for JF. In addition, K. R. RODDA (South Australian Research and Development Furthermore, it is possible to confidently assign Institute, Port Lincoln) and J. CARUSO (Melbourne these egg capsules to the hybodont shark Lonchidion Aquarium) provided data from their studies of extant shark humblei, a small durophagous nonmarine shark found egg capsules. Also, we are grateful to the late M. in the Chinle Formation at a closely adjacent locality. HELICKSON, Superintendent of Petrified Forest National This is only the second documented case of the direct Park for authorizing SRA to collect the fossils described here in the area under her jurisdiction and to her staff for assignment of a specific Palaeoxyris species to a assisting him with his field work. We thank J. HARRIS putative source as far as we have been able to as - (Boulder, Colorado and Chama, New Mexico) and W. certain, and it also confirms the general identification PARKER (Petrified Forest National Park, Arizona) for their of Palaeoxyris as the egg capsule of the hybodont constructive comments about an early version of this article. sharks. The manuscript was critically and constructively appraised Because of the facies characteristics of the News - by J. SCHNEIDER (Freiberg) and G. CUNY (Copenhagen). Field work was supported in part by a grant from the paper Rock Bed and adjacent strata, an allochthonous Petrified Forest Museum Association to SRA. The German burial on a floodplain resulting from flooding is the Research Foundation (DFG) supports the work of JF with most likely depositional setting for these egg capsules. the grant SCHN 408/14-1. Originally, they were probably laid elsewhere by L. humblei in special spawning grounds in vegetated zones alongside the banks of the stream that deposited References the Newspaper Rock Bed. There the capsules were ASH, S. R. (1970): Ferns from the Chinle Formation (Upper attached in pairs or more on a substrate such as a Triassic) in the Fort Wingate area, New Mexico. – piece of driftwood or more likely the submerged United States Geological Survey, Professional Paper, branches or stems of Equisetites or Neocalamites 613D: 1-40. plants whose remains occur so commonly at the same ASH, S. R. (1980): Upper Triassic floral zones of North locality (Table 1). America. – In: DILCHER, D. L. & TAYLOR, T. M. (Eds.): Biostratigraphy of fossil plants, 153-170; Stroudsburg The rarity of known egg capsules in the extensively (Dowden, Hutchinson & Ross). investigated Chinle Formation and their strong ATUNES,M.T., MAISEY, J.G., MARQUES, M.M., SCHAEFFER, similarity to cones of plants suggests that previous B. & THOMSON, K. S. (1990): Triassic fishes from the discoveries of egg capsules may have been mis - Cassange Depression (R. P. de Angola). – Ciências da identified and are still stored in private or public Terra (UNL) Número Especial, 1: 1-64. collections. The common occurrence of xenacanth AXSMITH, B. J. (2006): The first Mesozoic record of the enigmatic fossil Palaeoxyris from North America; shark remains in the overlying parts of the Chinle Chinle Formation, Petrified Forest National Park. – In: Formation suggests that the egg capsules type Fayolia PARKER W. G., IRMIS, R. B. & ASH, S. R. (Eds.): A should also be present there. We hope that this con- century of research at Petrified Forest National Park: The hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America 341

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ZIDEK, J. (1976): A new shark egg capsule from the Penn - Addresses of the authors: sylvanian of Oklahoma, and remarks on the chondrichthyan egg capsules in general. – Journal of Paleontology, JAN FISCHER, TU Bergakademie Freiberg, Geological In - 50: 907-915. stitute, Department of Palaeontology, Bernhard-von-Cotta street 2, 09599, Freiberg, Germany; Manuscript received: October 7th, 2008. e-mail: [email protected] Revised version accepted by the Stuttgart editor: January BRIAN J. AXSMITH, Department of Biology, Life Sciences 12th, 2009. Building, University of South Alabama, Mobile, Alabama, 36608, USA; e-mail: [email protected] SIDNEY R. ASH, Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico, 87131, USA; e-mail: [email protected]