DOI: 10.15468/7rrpbr
title: Janassid petalodonts (Chondrichthyes, Petalodontiformes, Janassidae) from the middle Mississippian (Viséan) Ste. Genevieve Formation, Mammoth Cave National Park, Kentucky, USA

description: This dataset contains the digitized treatments in Plazi based on the original journal article Hodnett, John-Paul M., Toomey, Rickard, Olson, Rickard, Tweet, Justin S., Santucci, Vincent L. (2023): Janassid petalodonts (Chondrichthyes, Petalodontiformes, Janassidae) from the middle Mississippian (Viséan) Ste. Genevieve Formation, Mammoth Cave National Park, Kentucky, USA. Historical Biology 36 (9): 1783-1792, DOI: 10.1080/08912963.2023.2231955, URL: http://dx.doi.org/10.1080/08912963.2023.2231955ABSTRACTARTICLE HISTORYIsolated teeth of two janassid petalodonts collected from cave passages within the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky represents the first record of this group of chondrichthyans from this formation. Anew janassid, Strigilodus tollesonae, gen et sp. nov., is recognised from isolated teeth, representing all tooth families, and are characterised by their rounded spoonlike cusps and V- to U-shaped lingual cristae. Janassa sp. is also present within the Joppa Member of the Ste. Genevieve Formation. Dental reconstructions are proposed for Strigilodus tollesonae and Cypripediodens cristatus, modelled after previous observations for Janassa dentitions. Strigilodus had a dental arrangement more similar to Janassa, while Cypripediodens was uniquely adapted for a possible extreme form of durophage feeding. We propose that within Janassidae, there were two unnamed subfamilies with Janassa and Strigilodus forming the Janassinae, while Cholodus, Cypripediodens, and Cavusodus forming Cholodinae subfam. nov.Received 18 May 2023 Accepted 27 June 2023KEYWORDSSte. Genevieve Formation; Mammoth Cave National Park; Mississippian; Carboniferous; petalodont; Janassidae; Chondrichthyes; Strigilodus; Janassaurn:lsid:zoobank.org:act: 763F8777-22A0-44CB-A520-CACCA49DF57Aurn:lsid:zoobank.org:act: 01EB9ACE-B3EA-4EA3-8F00-A158BAE4E1ACurn:lsid:zoobank.org:act: B83202DB-644A-4518-BC6F-E161E16C4553IntroductionPetalodontiformes is anenigmatic and diversechondrichthyan group witha richfossil record extending intoatleast the Early Mississippian (upper Tournasian) (Ginter et al. 2010). These chondrichthyans are known from numerous toothbased taxa as well as a few complete to near complete skeletons (Lund 1989; Ginter et al. 2010; Grogan et al. 2014; Lund et al. 2014). Early interpretations of this group placed petalodonts as elasmobranch chondrichthyans (MoyThomas 1939; Zangerl 1981; Hansen 1985), but recent work have placed Petalodontiformes within the Euchondrocephali with a potential sister relationship to Holocephali (Patterson 1965; Grogan et al. 2014; Lund et al. 2014). Presently, at least five families have been proposed within Petalodontiformes including: Belantseidae; Petalodontidae, Janassidae, Petalorhynchidae and Obruchevodidae (Lund 1989; Grogan et al. 2014; Lund et al. 2014). The family Pristodontidae, which has classically been placed within the Petalodontiformes (Hansen 1985; Ginter et al. 2010), has recently been suggested to be a sister group to the Petalodontiformes (Lund et al. 2014). Of interest here is the petalodont family Janassidae.The post-Mississippian JanassidaeThe family Janassidae is typified by Janassa and its type species J. bituminosa from the Middle Permian of Germany and United Kingdom. J. bituminosa is known from both isolated teeth, associated dentitions and partial to near complete skeletons with body impressions (Jaekel 1899; Malzahn 1968; Schaumberg 1979). The body fossils of J. bituminosa demonstrated it had a skate-like dorsoventrally compressed body plan with a long rostrum, ventral mouth, enlarged pectoral fins, ray-like pelvic fins and a tail ending in a round lobate caudal fin (Schaumberg 1979; Grogan et al. 2014). Aside from J. bituminosa, at least 14 additional species have been placed in the genus Janassa based on isolated teeth, with records extending from the Middle Mississippian to the middle Permian (Ginter et al. 2010). Among these 14 the Pennsylvanian to Permian Janassa species included J. angularis, J. emydinus, J. kochi, J. korni, J. linguaeformis, J. maxima, J. oblongus, J. strigilina, J. unguicula and J. unguiformis (Ginter et al 2010). Lund et al. (2014) has recently argued that ‘ Janassa ’ (‘ Ctenoptychius ’) korni, which is known from a number of partial to near complete individuals and dentitions (Brandt 1996, 2009), was not a janassid but was more closely related to Petalorhynchus. Petalorhynchus was previously placed in Janassidae (Ginter et al. 2010) but has recently been placed in its own distinct family, the Petalorhynchidae (Lund et al. 2014). Recently, Itano (2023) resurrected the use of Peltodus unguiformis (Newberry and Worthen 1870) which previously was placed in Janassa by Woodward (1889) and was used to identify a number of Janassa -like teeth in the Late Pennsylvanian of Illinois and the Middle Permian of Wyoming (Eastman 1903; Branson 1916, 1933). Itano (2023) noted that P. unguiformis had teeth that resembled Janassa but lacked an extended, ridged lingual heel, having only an ìmbricated belt’ (St. John and Worthen 1875, p. 410), and the angle between the base and the lingual heel is not close to 90°. This led Itano (2023) to conclude that the inclusion of P. unguiformis as Janassa by Woodward (1889) was erroneous and this taxon should be placed in another petalodont family.Fissodus, known from four species, was another taxon placed into the Janassidae (Hansen 1985; Ginter et al. 2010). Lund et al. (2014) demonstrated that the various species of Fissodus, which are known primarily from isolated bifid teeth, may belong to several other petalodonts that also have a ‘Fissodus-type’ bifid lower symphyseal tooth. Lund et al. (2014) also suggested the type species to Fissodus, F. bifidus (St. John and Worthen 1875) should not be included in the family Janassidae as well. Itano (2023) recently verified that the Late Pennsylvanian Cholodus inaequalis (St. John and Worthen 1875) was aspecies to beincluded with the Janassidae and may haverelationships with two Mississippian species discussed further.The Mississippian JanassidaeThe Mississippian record of Janassidae extends from the Middle Mississippian (Viséan) to Latest Mississippian (Serpukhovian). Presently, three species of Janassa are recognised during the Mississippian period from isolated teeth: J. imbricata (M’Coy 1848) from the Viséan of the Mountain Limestone of Derbyshire, England, J. clavata (M’Coy 1855) from the Serpukhovian Carboniferous Limestones of England, Scotland and Ireland, and J. clarki (Lund 1989) from the Serpukhovian Bear Gulch Limestone of Montana. Duffin and Ward (2017) described a janassid taxon with a rather derived dentition, Cypripediodens cristatus. Cypripediodens has a well-developed lingual cusp that evolved from the lingual cristae as well as additional lingual denticles and a broad labial base; it was collected from the Middle Mississippian Eyam Limestone Formation in Derbyshire United Kingdom (Duffin and Ward 2017). Recently, Itano (2023) described Cavusodus whitei from a few isolated teeth collected from the Middle-Late Mississippian Bangor, Monteagle and Pride Mountain formations of north-western Alabama. Itano (2023) proposed that Cavusodus was more closely related to Cypripediodens and Cholodus than to Janassa. Here, we report of a new Middle Mississippian record of Janassa and a new janassid taxon from the Joppa Member of the Ste. Genevieve Formation of Mammoth Cave National Park, Kentucky found during palaeontological resource inventory and monitoring within the park.Institutional AbbreviationsMACA: Mammoth Cave National Park, Kentucky; NHMUK: Natural History Museum, London, England.Geological settingThe Mississippian period strata found at Mammoth Cave National Park represent one of the southeasternmost portions of the ancient marine Illinois Basin (Palmer 1981) (Figure 1). The Illinois Basin is historically significant to early American palaeoichthyology as a large number of middle to late Palaeozoic fish fossils were collected and described from within this basin in other states such as Missouri, Illinois, Iowa and Indiana (Newberry and Worthen 1870; St. John and Worthen 1875, 1883). At the time, these early collections were widely compared with similar fossils from Europe, which formed the basis for modern Palaeozoic chondrichthyan palaeoichthyology. The Ste. Genevieve Formation stratigraphically overlies the St. Louis Formation and is recognised as Viséan/lower Chesterian (Thompson 2001). The Ste. Genevieve is locally 110– 120-feet thick. The majority of the passages of the Mammoth Cave System are developed in the Ste. Genevieve Formation (Palmer 1981). This horizon consists primarily of light grey limestones and dolomitic limestones with the upper beds alternate thin dark, silty, granular limestones (Palmer 1981). The large number of cave passages cutting through the Ste. Genevieve Formation led to well exposed fossils and fossil bearing beds. The multiple cave passage localities within Mammoth Cave National Park document a prolific fossil record (Figure 2). The Joppa Member of the Ste. Genevieve Formation at Mammoth Cave contains several biostrome beds rich with horn corals, bryozoans, brachiopods and echinoderms (mainly crinoids and blastoids), separated by somewhat less fossiliferous zones. Chondrichthyan teeth, dermal spines and denticles, are common within multiple horizons within the Joppa Member at Mammoth Cave and isolated to partially articulated skeletal cartilage also occurs. Presently, over 60 taxa of cartilaginous fishes have been identified from the Joppa Member.Materials and methodsThefield work for the Mammoth Cave National Park Palaeontological Resource Inventory (PRI) commenced in November of 2019. At present, over 25 caves and cave passages have been surveyed fully or in part, as part of a concentrated effort to document, collect and identify Mississippian vertebrate fossils. Space in field packs limits the amount of collecting gear that can safely traverse cave passages. That limitation and cave passage size and shape make collecting a challenge in some passages. Some sites require a rock saw or hammer and chisel to remove specimens while limiting breakage; in other passages, specimens can easily be teased out of the cave surfaces with a pointed tool (such as a dental pick). Many of these sites have low ceilings requiring crawling for long distances on hands and knees, and at times, belly crawling. The fish fossils are commonly encountered in the cave ceilings or walls of the cave passages.To protect the fossils for transport to the surface, each fossil is wrapped either in paper towel or toilet paper and placed on a hardsided container. We use screw-capped sampling tubes lined with cotton balls for collecting smaller fossil teeth. Our primary method is to removeall butone cotton ball, carefully teasethefossil fromthe cave surface (often from the cave ceiling) into the tube, and place a cotton ball on top and continue on to the next specimen. We repeat this methoduntil the tube is full and record ourlocality information on the tube. This method is extremely useful in areas where there is a high concentration of vertebrate fossils in a small area.Photography of the fossils presented here were captured with an AmScope camera mounted on a stereoscope microscope with a metric scale bar. Figures were created with Adobe Illustrator 2023 and Photoshop 2023, respectively. We refer to Duffin and Ward (2017, fig. 3) and Itano (2023, fig. 1) for anatomical nomenclature and diagrams of anatomical features.Systematic PalaeontologyClass Chondrichthyes Huxley 1880Subclass Euchondrocephali Lund and Grogan 1997Order Petalodontiformes Patterson 1965Family Janassidae Jaekel 1899