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N. Jb. Geol. Paläont. Abh. 2007, vol. 244/1, p.1– 8, Stuttgart, April 2007, published online 2007

Pennsylvanian (Late Carboniferous) chondrichthyans from the LaSalle Limestone Member (Bond Formation) of Illinois, USA Stephen L. Brusatte, Chicago With 5 figures

BRUSATTE, S. L. (2007): Pennsylvanian (Late Carboniferous) chondrichthyans from the LaSalle Limestone Member (Bond Formation) of Illinois, USA. – N. Jb. Geol. Paläont. Abh., 244: 1–8; Stuttgart. Abstract: Chondrichthyan teeth are common fossils in late Paleozoic rock units worldwide, and potentially useful in biogeographic, biostratigraphic, paleoecological, and taphonomic studies. Here I present a brief description of a newly-discovered chondrichthyan macrofauna from the LaSalle Limestone Member of the Bond Formation (Missourian, Upper Pennsylvanian, Late Carboniferous) of La Salle County, Illinois. Recent fieldwork has yielded isolated remains of four chondrichthyan tooth taxa (Petalodus ohioensis, Peripristis semicircularis, Helodus cf. simplex, Deltodus angularis), which are briefly described and compared to similar taxa from across the globe. This is the first publication to provide explicit stratigraphic and locality data for a chondrichthyan fauna from Illinois, and raises potential for future discoveries of chondrichthyan tooth and body fossils. Key words: Chondrichthyes, Petalodontida, Elasmobranchii, Holocephali, Carboniferous, Pennsylvanian, Paleozoic, Illinois, biogeography, biostratigraphy.

1. Introduction Isolated macroscopic chondrichthyan teeth, spines, and dermal denticles are common fossils in late Paleozoic rock units worldwide. Several Pennsylvanian (Late Carboniferous) chondrichthyan genera were originally described from Illinois (United States) during the early state geological surveys of the late nineteenth century (NEWBERRY & WORTHEN 1866, 1870; ST. JOHN & WORTHEN 1875, 1883; HAY 1885; BRANSON 1905), including teeth and spines of petalodontiform and cochliodontid chondrichthyans. However, as many of these specimens were collected prior to any detailed geological analyses of the Illinois Basin, precise stratigraphic and locality data are missing for most Pennsylvanian chondrichthyans from Illinois. In recent years, much attention has been devoted to the vertebrate faunas of the DesmoiDOI: 10.1127/0077-7749/2007/0244-0001

nesian Mazon Creek deposits (SHABICA & HAY 1997) and Mecca and Logan Quarry Shales (ZANGERL & RICHARDSON 1963; WILLIAMS 1985) of Illinois. This work has produced comprehensive descriptions of well-preserved chondrichthyan body fossils, but has largely ignored isolated macroscopic teeth, spines, and denticles. In particular, no published reports have attempted to place Illinois chondrichthyan tooth faunas in a stratigraphic context, and little consideration has been given to the state’s Late Pennsylvanian vertebrates. Here I present a brief description of a newly discovered macroscopic vertebrate fauna from the LaSalle Limestone Member of the Bond Formation (Missourian, Upper Pennsylvanian, Late Carboniferous) of La Salle County, Illinois (Fig. 1). Vertebrate material from the general vicinity of La Salle County was originally described in the late nineteenth century, 0077-7749/07/0244-0001 $ 2.00 © 2007 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart

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Fig. 1. Location map and representative stratigraphic section (measured at the Orlando Smith Road Outcrop) of the La Salle Limestone. The general collecting area is denoted by a rectangle.

and includes the type specimens of the holocephalians Psephodus actus BRANSON, 1905; Deltodus angularis NEWBERRY & WORTHEN, 1866; and Cymatodus oblongus NEWBERRY & WORTHEN, 1870, as well as specimens of Lophodus ROMANOVSKY, 1864; Sandalodus NEWBERRY & WORTHEN, 1866; Helodus AGASSIZ, 1838; Acondylacanthus ST. JOHN & WORTHEN, 1875; Vaticinodus ST. JOHN & WORTHEN, 1883; and Petalodus OWEN, 1840. While these specimens were likely collected from the LaSalle Limestone Member, they were usually described as coming from “the limestone near La Salle, Illinois,” and thus any specific stratigraphic or locality data is unknown. Recent fieldwork in the LaSalle Limestone has yielded four chondrichthyan tooth taxa (Petalodus ohioensis SAFFORD, 1853, Peripristis semicircularis NEWBERRY & WORTHEN, 1866, Deltodus angularis MORRIS & ROBERTS, 1862, and Helodus cf. simplex AGASSIZ, 1838) as well as isolated fish scales and bone fragments. In general, this assemblage is similar to faunas known from Arizona (ELLIOTT et al. 2004), Colorado (ITANO et al. 2003), New Mexico (LUCAS & ESTEP 2000; ZIDEK & KIETZKE 1993), and Ohio (HANSEN 1996), and adds another record to the growing list of localities worldwide that preserve comparable late Paleozoic chondrichthyan assemblages.

Institutional abbreviations: FMNH, Field Museum of Natural History, Chicago, Illinois; UCRC, University of Chicago Research Collection, Chicago, Illinois.

2. Geological setting The LaSalle Limestone Member of the Bond Formation crops out frequently in both La Salle and Livingston Counties, where it is extensively mined for Portland cement (Fig. 1). This unit is characterized by thick benches of algal bank limestone alternating with thinner anoxic black shales (FRASER 1991). Fossils are abundant in this unit, and include brachiopods (BRUSATTE 2004), crinoids (STRIMPLE & MOORE 1971), and other invertebrates. Sites visited for this study are located in La Salle County, and include the Buzzi Unichem Quarry (NE 1/4 , SE 1/4 of Sec 36, T33N, R1E La Salle Twp), an outcrop along Orlando Smith Road (SE 1/4 , SE 1/4 of Sec 22, T33N, R1E La Salle Twp), and an abandoned quarry near Bailey Falls (SW 1/4 Sec 6, T32N, R2E Vermilion Twp). Rigorous correlations between different measured sections are currently premature, but the Orlando Smith Road outcrop is stratigraphically higher than the Buzzi Unichem outcrops (BRUSATTE, unpubl. data).

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Fig. 2. Tooth of Petalodus ohioensis SAFFORD, 1853 (FMNH PF 14202) in lingual (A) and labial (B) views. Scale bar equals 1 cm.

3. Systematic paleontology Chondrichthyes HUXLEY, 1880 Petalodontida ZANGERL, 1981 Petalodontidae NEWBERRY & WORTHEN, 1866 Petalodus OWEN, 1840

Petalodus ohioensis SAFFORD, 1853 Fig. 2A-B Material: Nearly complete tooth from the Bailey Falls Section (FMNH PF 14202) and nearly complete crown from the Orlando Smith Road Outcrop (UCRC PV4a). A total of 29 crown fragments from the Buzzi Unichem Quarry (UCRC PV4) clearly represent Petalodus, and are provisionally referred to P. cf. ohioensis based on overall morphology and stratigraphic position (see HANSEN 1985). Description: FMNH PF 14202 (Fig. 2) is a complete tooth, measuring 58 mm in dorsoventral depth and 50 mm in mesiodistal width. It is labiolingually compressed and slightly sigmoid in mesial view. Lingually, the crown is bordered ventrally by a band of imbricating ridges, which is narrow as is diagnostic for P. ohioensis (HANSEN 1985; DALLA VECCHIA 1988). The remaining specimens are highly fragmented. Because of their fragmentary nature, specimens from the Buzzi Unichem Quarry (UCRC PV4) generally do not preserve details of the imbricated ridges, and thus are not clearly diagnostic at the species level. However, based on their general resemblance to P. ohioensis, as well as their stratigraphic position in the Pennsylvanian (see below), these specimens are referred to P. cf. ohioensis.

Discussion: Petalodus is among the most distinctive and common late Paleozoic chondrichthyan tooth genera, and ranges in age from the Meramecian (Late Mississippian) to the Wolfcampian (Early Permian). Although several species have been assigned to this genus based on subtle shape differences, today many of these are regarded as junior synonyms of two widespread species: P. acuminatus AGASSIZ 1838, the dominant Late Mississippian (Early Carboniferous) form, and P. ohioensis, which is wellnown from Pennsylvanian (Late Carboniferous) and Early Permian strata (HANSEN 1985). One notable invalid species is P. securiger, a taxon established by HAY (1885) based on specimens found near La Salle, Illinois, and currently regarded as a junior synonym of P. ohioensis (HANSEN 1985). Specimens of Petalodus are known worldwide, and have been described from Arizona (ELLIOTT et al. 2004), New Mexico (ZIDEK & KIETZKE 1993; LUCAS & ESTEP 2000), Kansas (ROBB 2003), Colorado (ITANO et al. 2003), Texas (MCNULTY 1963), Oklahoma (ZIDEK 1973), Ohio (HANSEN 1996), Slovenia (RAMOVSˇ 1997), Italy (DALLA VECCHIA 1988), and other locales in Europe and Asia (HANSEN 1985).

Elasmobranchii BONAPARTE, 1838 Pristodontidae WOODWARD, 1889 Peripristis ST. JOHN, 1870 Peripristis semicircularis NEWBERRY & WORTHEN, 1866 Fig. 3 A Material: One nearly complete tooth (UCRC PV5) from the Orlando Smith Road Outcrop.

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Fig. 3. Chondrichthyan teeth from the LaSalle Limestone. (A) Peripristis semicircularis NEWBERRY & WORTHEN , 1866 (UCRC PV5) in labial view. (B) Helodus cf. simplex AGASSIZ, 1833-43 (UCRC PV6) in occlusal view. Scale bars equal 1 cm.

Description: The lone recovered specimen (Fig. 3A) is relatively complete, but eroded on one margin. It is approximately 18 mm wide mesiodistally, and 11 mm deep dorsoventrally. Labially, the crown is divided into five triangular, lobate cusps that decrease in size toward the mesial and distal margins, as is characteristic of P. semicircularis (HANSEN 1985). As the specimen is imbedded in a block of limestone, only the labial surface is exposed. Thus, the unique lingual shelf and pit that characterizes P. semicircularis and other pristodontids is not visible. However, it is evident that the specimen lacks a distinct series of labial imbricating ridges, as in all pristodontids. Discussion: As with Petalodus, Peripristis is a common North American late Paleozoic fossil that ranges in age from the Late Mississippian to the Early Permian. Along with a range of other forms, Peripristis belongs to the Pristodontidae, a group of petalodontiform chondrichthyans characterized by lobate teeth with a prominent lingual shelf and pit (ZANGERL 1981; HANSEN 1985). Specimens of Peripristis have been reported from several Pennsylvanian units, including locales in Colorado (ITANO et al. 2003), New Mexico (ZIDEK & KIETZKE 1993), and Ohio (HANSEN 1996). It has not been reported outside North America.

Holocephali BONAPARTE, 1832 Helodontiformes PATTERSON, 1965 Helodontidae PATTERSON, 1965 Helodus AGASSIZ, 1838 Helodus cf. simplex AGASSIZ, 1838 Fig. 3 B Material: One nearly complete tooth from the Buzzi Unichem Quarry (UCRC PV6).

Description: The single collected tooth (Fig. 3B) measures 9 mm in mesiodistal width and 20 mm in labiolingual length. The crown is finely punctate, and rises at its center into a low, bulbous projection. The mesial and distal edges are both marked by fine raised lineations that may have formed an articulation with adjacent teeth. This morphology is diagnostic of Helodus, but specific characters of H. simplex are not apparent, although the overall morphology of this specimen closely matches published figures of H. simplex (e.g., STAHL 1999). Thus, this tooth is referred to Helodus cf. simplex. D i s c u s s i o n : This genus is known from Devonian-Early Permian units worldwide (STAHL 1999), and is especially common in the Mississippian of the Midwestern United States. Teeth of Helodus simplex are very similar to those of Psephodus, a genus reported from the La Salle area by BRANSON (1905).

Cochliodontiformes OBRUCHEV, 1953 Cochliodontidae OWEN, 1867 Deltodus MORRIS & ROBERTS, 1862 Deltodus angularis NEWBERRY & WORTHEN, 1866 Fig. 4A-B Material: Thirty-six tooth plate fragments (UCRC PV7) from the Buzzi Unichem Quarry. Description: The material consists of several crown fragments in a variable state of preservation. Some specimens are noticeably fragmented, while others are nearly complete. The crowns are convex, with a surface that is generally smooth but finely punctate. Some specimens are marked with a distinct convex ridge running along the long axis of the tooth, and faint depressions and wear facets are visible on some of the tooth plates. One specimen shows faint

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Fig. 4. Teeth of Deltodus angularis NEWBERRY & WORTHEN, 1866 in occlusal view. (A) UCRC PV7a. (B) UCRC PV7 b. Scale bar equals 1 cm.

radial zonations, which may represent growth lines, while two fragments preserve a portion of the root, which is slightly inset relative to the crown. The small size, teardrop to triangular shape, and lack of transverse corrugations are diagnostic of D. angularis relative to other species of Deltodus (e. g., D. sublaevis: see STAHL 1999; STAHL & HANSEN 2000; ELLIOTT et al. 2004). Discussion: One of the most characteristic Late Paleozoic chondrichthyan genera, Deltodus, is known from several deposits worldwide, including those in Arizona (ELLIOTT et al. 2004), Colorado (ITANO et al. 2003), West Virginia (LUND et al. 1979), Ohio (HANSEN 1996), Oklahoma (ZIDEK 1973), and Wyoming (BRANSON 1916), as well as locales in Thailand, France, England, Ireland, Belgium, Russia, and Australia (STAHL 1999). This genus is commonly represented by isolated and fragmentary tooth plates, which indicate a durophagous diet.

4. Other vertebrate fossils Additional vertebrate fossils recovered from the LaSalle Limestone include several indeterminate osteichthyan scales and a possible three-dimensional chondrichthyan braincase (FMNH PF 8744) (Fig. 5). This specimen clearly preserves prismatic calcified cartilage, a feature of chondrichthyans, and has an outline consistent with that of a braincase, but few other details are evident. Tetrapod material has been reported, including several long bones discovered in a lens deposit and a complete femur discovered during a prospecting trip led by the Earth Science Club of Northern Illinois, but is not available for study.

5. Discussion and conclusions This paper is the first published description of the chondrichthyan tooth fauna of a particular Pennsylvanian unit in Illinois. While other descriptions of Illinois chondrichthyan fossils have been published (e. g. NEWBERRY & WORTHEN 1866, 1870; ST. JOHN & WORTHEN 1875, 1883; ST. JOHN 1885; BRANSON 1905), none include detailed stratigraphic and locality data. These omissions hinder any attempts to determine precise stratigraphic and geographic ranges for chondrichthyan taxa in Illinois, and thus make reliable comparisons to similar faunas difficult. As shark teeth are common fossils in many late Paleozoic deposits, they are potentially useful in biogeographic, biostratigraphic, paleoecological, and taphonomic studies. HANSEN (1985) suggested that petalodont teeth from the mid-continental United States may permit biostratigraphic zonation to at least the series level, but then lamented the lack of detailed locality and stratigraphic data for most taxa. This problem has been addressed in a handful of recent studies, including those of LUCAS & ESTEP (2000), ITANO et al. (2003), and ELLIOTT et al. (2004), which have described Pennsylvanian chondrichthyan tooth faunas within a stratigraphic context. But, the fact that this note is the first such attempt to carefully describe a late Paleozoic tooth fauna from Illinois strongly attests that much work remains to be done. Comparison of the LaSalle Limestone chondrichthyan fauna with other global assemblages is currently difficult, as only preliminary fieldwork has been conducted in Illinois. Thus, detailed comparisons of

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Fig. 5. Indeterminate chondrichthyan braincase (FMNH PF 8744). Scale bar equals 1 cm.

the diversity and relative abundance of taxa between the LaSalle Limestone and other formations is not possible at the moment. However, the LaSalle Limestone shares chondrichthyan tooth taxa with similarage formations from across the United States, as well as Europe and Asia (e. g., HANSEN 1985; STAHL 1999; LUCAS & ESTEP 2000; ITANO et al. 2003; ELLIOTT et al. 2004). This adds to growing evidence for the cosmopolitan nature of chondrichthyan faunas during the Pennsylvanian (Late Carboniferous). However, some regional differences in faunas are apparent. For example, although Petalodus and Deltodus are known from across North America and from sites in Europe and Asia, Peripristis has not been reported outside North America. In addition to yielding the fossils described in this note, fieldwork in the LaSalle Limestone Member has revealed potential for future vertebrate discoveries. The anoxic black shales that alternate with the more prominent limestone beds are similar in lithology to the fossiliferous Mecca and Logan Quarry Shales, which have produced a diverse assemblage of wellpreserved chondrichthyan body fossils (WILLIAMS 1985). Additionally, although most Pennsylvanian tetrapods are found within fluvial-deltaic and lake deposits (DIMICHELE & HOOK 1992), the discovery of isolated tetrapod remains within the LaSalle Limestone Member suggests a potential for future discoveries. As paleontological studies of the La Salle Limestone Member have so far been limited, additional fieldwork is sure to uncover new specimens.

Acknowledgements I thank J. JAKUPCAK for introducing me to the LaSalle Limestone and for collaborating on an ongoing cooperative fieldwork project. F. DALLA VECCHIA and R. SOLER-GIJO´N are thanked for their thoughtful reviews which greatly improved the manuscript, and D. ELLIOTT and M. FRIEDMAN are thanked for discussion and comments on an earlier draft of this paper. J. CATALANI, J. JAKUPCAK, and B. MASEK are acknowledged for discovering some of the material described herein. I thank R. FITCH and T. ZMUDKA for quarry access, P. SERENO, W. TAYLOR, and R. VODDEN (UCRC) and B. SIMPSON (FMNH) for access to collections, C. ABRACZINSKAS for assistance with figures, and D. CARLSON, M. COATES, R. JACOBSON, M. LABARBERA, M. PHILLIPS, and N. SHUBIN for discussion.

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Manuscript received: August 23rd, 2006. Revised version accepted: January 3rd, 2007. Address of the author: STEPHEN L. BRUSATTE, Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago, Illinois 60637, USA; E-mail: [email protected] Current Address: Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom; E-mail: [email protected]