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Fossil Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska

Fossil Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska

DePaul Discoveries

Volume 2 Issue 1 Article 6

2013

Fossil Marine Vertebrates from the Middle Part of the Upper Graneros Shale in Southeastern

Alexander D. Meglei [email protected]

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Recommended Citation Meglei, Alexander D. (2013) " Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska," DePaul Discoveries: Vol. 2 : Iss. 1 , Article 6. Available at: https://via.library.depaul.edu/depaul-disc/vol2/iss1/6

This Article is brought to you for free and open access by the College of Science and Health at Via Sapientiae. It has been accepted for inclusion in DePaul Discoveries by an authorized editor of Via Sapientiae. For more information, please contact [email protected]. Fossil Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska

Acknowledgements Faculty Advisor: Dr. Kenshu Shimada; Department of Environmental Science and Studies and Department of Biological Sciences

This article is available in DePaul Discoveries: https://via.library.depaul.edu/depaul-disc/vol2/iss1/6 Meglei: Fossil Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska DEPAUL DISCOVERIES (2O13)

Fossil Marine Vertebrates from the Middle Part of the Upper Cretaceous Graneros Shale in Southeastern Nebraska

Alexander D. Meglei* Department of Biological Sciences

ABSTRACT The Graneros Shale is a rock unit formed in the of . In this study, I report an assemblage of fossil vertebrates from the middle portion of the Graneros Shale in southeastern Nebraska. The estimated age of this fauna is about 97 million old, and it is dominated by carnivores that consist of at least 11 taxa, comprising of eight , one bony fish, and two reptilians ( and plesiosaur). The fauna includes taxa indicative of a nearshore, but fully marine, environment that do not contradict with previous paleoenvironmental inferences made for the Graneros Shale. This study is important because it represents the first collective faunal study of fossil vertebrates from the mid-Graneros Shale at a single locality.

INTRODUCTION and rays) and 10 osteichthyan (bony fish) taxa (Jansen et of extinct organisms provide insight into the al., in press). environmental conditions of the past. The Graneros Shale (Fig. 1A) is a Late Cretaceous rock formation deposited Kirkland’s (1989) brief report also included one other in the Western Interior Seaway (Hattin, 1965; for specific fauna from the Graneros Shale at the same locality age estimation, see below), in which vertebrate fossils, in southeastern Nebraska focusing only on its such as those of fish and plesiosaurs, are known to chondrichthyan components. The fauna is from the occur (e.g., Welles, 1970; Witzke, 1981; Russell, 1988; middle part of the formation below the X-, Schumacher and Everhart, 2005). However, while but the entire fauna has remained unstudied. In this previous reports on fossil vertebrates from the Graneros paper, I formally describe the vertebrate assemblage. My Shale are scattered in literature, the only collective study goal is two-fold: 1) to formally describe the taxonomic on the Graneros vertebrate fauna is that of the fish fauna components of the fauna, and 2) to discuss the from the uppermost part of the formation in southeastern paleoenvironment of the area during its deposition. Nebraska reported by Jansen et al. (in press) who built

upon a brief account reported by Kirkland (1989). The LOCALITY AND STRATIGRAPHY fauna came from the uppermost horizon within the The fossils described in this paper were collected from formation, approximately 50 cm above a 30–45 cm thick a roadcut along the east side of State Highway 15, altered volcanic ash layer known as the X-bentonite, and approximately 1.6 km north of the -Nebraska was found to contain at least 14 chondrichthyan (sharks boarder. As in Kansas (Hattin, 1965), the Graneros Shale at the locality is represented largely by dark gray, * Faculty Advisor: Dr. Kenshu Shimada; Department of Environmental non-calcareous, silty-clayey shale and contains the Science and Studies and Department of Biological Sciences X-bentonite approximately 50 cm below the contact Project completion: Winter Quarter, 2013 Author contact: [email protected] between the Graneros Shale and the conformably

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overlying Greenhorn (see also Hattin, 1975). DISCUSSION Although the exact stratigraphic horizon or range where Russell (1988) provided a summary of Cretaceous marine the fossils described in this present study occurred faunas of North America and listed several vertebrate is uncertain, they all came from the typical dark-gray taxa from unknown stratigraphic horizons within the silty-clayey portion of the Graneros Shale below the Graneros Shale in multiple areas (, Nebraska, Kansas, X-bentonite. Whereas the Graneros Shale is about 10 m , and ) known at that time. They thick in the adjacent area (e.g., Kansas), several meters of included occidentalis (), the Graneros Shale is present at the locality. Because the sp. (bony fish), indet. (plesiosaur), fossils described here come from the middle portion of Thalassomedon haningtoni (plesiosaur), Coelosuchus the formation, I refer to the vertebrate assemblage as the reedi (crocodilian), and americanis ‘mid-Graneros fauna’ for the purpose of this study. () (Russell, 1988; see Schumacher and Everhart, 2005, for additional information on plesiosaurs

MATERIALS AND METHODS from the Graneros Shale) Subsequently, Kirkland (1989) Fossil specimens were collected by James I. Kirkland in reported the occurrence of the following four shark taxa the late 1980s soon after the rocks at the locality became from the formation: semiplcatus, freshly exposed due to the construction of Highway mantelli, falcatus, and Odontaspis sp. My 15 (Fig. 1B). All fossils are poorly preserved and were present study that identifies 11 taxa (Table 1) represents collected via surface picking, and thus, it is likely that the re-examination of Kirkland’s (1989) material based the fossil assemblage involves collecting bias towards on an updated taxonomic scheme. It constitutes the larger fossils. Prior to my study, the specimens remained first collective work of the vertebrate fauna from the uncatalogued in the collection of the University of mid-Graneros Shale with more constrained geographic Nebraska State Museum (UNSM), Lincoln, Nebraska. and stratigraphic ranges than Russell’s (1988) faunal The specimens were subsequently loaned to DePaul summary. University (to K. Shimada) for the purpose of my study. Taxonomic identifications were conducted based on Although the exact stratigraphic horizon within the published literature (e.g., Shimada et al., 2006; Cumbaa middle section of the Graneros Shale is uncertain, the et al., 2010). mid-Graneros fauna comes from below the X-bentonite and not immediately above the underlying Dakota

RESULTS Sandstone. 40Ar/39Ar age dating analysis on the Table 1 lists all the vertebrate taxa and specimens X-bentonite in an adjacent area (west-central Kansas) represented in the mid-Graneros fauna at the locality. yielded a reliable plateau age of 95.53 ± 0.15 million years The fauna consists of a total of 11 taxa, comprising ago (Ma) (Shimada et al., 2006). Based on invertebrate eight chondrichthyan and one osteichthyan fishes as evidence, the upper part of the Dakota Sandstone is well as two reptilian taxa. The most common taxon inferred to be approximately 99.6Ma (Cobban et al., 2006, is Archaeolamna sp. Although the exact taxonomic fig. 1). Therefore, my mid-Graneros fauna is interpreted identification of some of the taxa remains uncertain, all to be about 97 ± 1 Ma (i.e., middle Middle ). other decisively identified vertebrate taxa reported here have been documented from other similar aged (mid- The underlying Dakota Sandstone is inferred to have Cenomanian; see below) localities in North America (e.g., been deposited in a marginal-marine setting in which Welton and Farish, 1993; Cumbaa et al., 2006; Shimada the Graneros Shale represents the onset of a major et al., 2006; Shimada and Martin, 2008; Underwood and transgressive phase of the Western Interior Seaway Cumbaa, 2010; Cumbaa et al., 2010; Everhart, 2011). (Hattin et al., 1987). Although the exact taxonomic

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identity of the chelonian remains (Fig. 2J) is uncertain, also served as food for probable small to medium-sized other vertebrates in my fauna are fully marine taxa, carnivores such as Caracharias and Archaeolamna (e.g., indicating that the locality was in a true marine condition see Shimada et al., 2006). However, the fact that the fauna without any apparent terrestrial influence during the is dominated by carnivorous taxa suggests that there deposition of the mid-Graneros Shale. However, the must have been many more small prey present fact that the mid-Graneros Shale consists of terrigenous in abundance in the Western Interior Seaway during the sediments (land derived particles) (Hattin, 1965) and deposition of the mid-Graneros Shale. that my fauna includes a hybodont shark characteristic of a near-shore environment (see Welton and Farish, CONCLUSION 1993) indicates that the eastern shoreline of the Western My study represents the first collective description of Interior Seaway was still not so far away from the locality vertebrate fauna during the deposition of mid-Graneros and that the locality at that time represented a shallow- Shale in the Late Cretaceous Western Interior Seaway water environment relative to the ocean during the of North America. A total of 11 taxa are identified, deposition of the overlying in the comprising eight chondrichthyan (Hybodontidae, area (see also Hattin, 1975; Hattin et al., 1987). Squalicorax, Caracharias, Archaeolamna, Cretodus, , , and Cretoxyrhina), one One notable characteristic of the fauna is the scarcity osteichthyan (), and two reptilian ( of Squalicorax and Enchodus that are quite common in and Chelonia) taxa. Whereas the estimated age of this other mid-Cenomanian localities (e.g., Shimada et al., fauna is about 97 Ma, the fauna includes taxa indicative 2006; Shimada and Martin, 2008; Gallardo et al., in press). of a nearshore, but fully marine, environment that is Their underrepresentation in my sample may be due consistent with previous paleoenvironmental inferences to a collecting bias towards larger specimens because for the Graneros Shale based on lithological and remains of these taxa are generally small. Nevertheless, invertebrate evidence (Hattin, 1965, 1975). Although the scarcity of these two taxa also in a fauna with well- the taxonomic representation of the fauna most likely sampled small taxa from the uppermost part of the suffers from collecting bias towards larger taxa, the Graneros Shale (Jansen et al., in press) is intriguing. This fauna is dominated by carnivorous taxa, suggesting the observation could mean that Squalicorax and Enchodus abundant existence of small prey taxa in the sea during preferred offshore environments during the deposition the deposition of the mid-Graneros Shale. of at least middle-upper portion of the Graneros Shale,

but more thorough sampling of vertebrate remains from ACKNOWLEDGEMENTS the entire formation is necessary to substantiate this I thank G. R. Corner (UNSM) for the loan of the specimens proposition. for the purpose of this study, J. I. Kirkland (Utah Geological Survey) for providing useful information, With a probable exception of Chelonia indet., all and K. Shimada (DePaul University) for support and vertebrates from the mid-Graneros Shale reported here guidance. are considered carnivores or opportunistic feeders, . including (e.g., see Schwimmer et al., 1997; Cicimurri and Everhart, 2001; Shimada, 2008; Shimada et al., 2010). Enchodus, a probable small predator that possibly fed on soft-bodied invertebrates such as squid (Grandstaff and Parris, 1990), is the smallest taxon represented in the mid-Graneros fauna and could have

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FIGURE 1

Simplified Upper Cretaceous stratigraphy in southeastern Nebraska (A; gray line indicates middle portion of Graneros Shale focused on in this paper) and photograph of southeastern Nebraska locality described here (B; photograph taken in April 2011).

Meglei (Page 11)

FIGURE 2 TABLE 1 Table 1. List of vertebrate taxa from mid-Graneros Shale in southeastern Nebraska along with Representative remains from mid-Graneros Shale in southeastern their sampleList ofsizes vertebrate and catalogue taxa numbers.from mid-Graneros Shale in southeastern Nebraska

Nebraska. A, Hybodontidae indet. (dorsal fin spine; UNSM along with their sample sizes and catalogue numbers. 127900); B, Squalicorax curvatus (one of five teeth in UNSM 127901); C, amonensis (one of four teeth in UNSM 127902); D, Archaeolamna cf. A. kopingensis (one of nine teeth in UNSM 127903); E, Cretodus semiplicatus (one of four teeth in UNSM 127904); F, Cretalamna appendiculta (one of four teeth in UNSM 127905); G, Cardabiodon sp. (; UNSM 127906); H, Cretoxyrhina mantelli (one of two teeth in UNSM 127907); I, Enchodus gladiolus (right palatine ; UNSM 127908); J, Chelonia indet. (one of shell fragments in UNSM 127910); K, Plesiosauria indet. (tooth; UNSM 127909). Orientations: A, left = anterior view, middle = posterior view, right = left lateral view; B-H, left = lingual view, right = labial view; I, lingual view (anterior

to right); J, exterior view; K, from left to right = labial, anterior, posterior, and lingual views. Bar scale = 10 mm. .

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LITERATURE CITED

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Cobban, W.A., Walaszczyk, I., Obradovich, J.D. and McKinney, K.C. 2006. Schumacher, B.A. and Everhart, M.J. 2005. A stratigraphic and taxonomic A USG zonal table for the Upper Cretaceous middle Cenomanian- review of plesiosaurs from the old “Fort Benton Group” of central of the Western Interior of the based Kansas: a new assessment of old records. Paludicola 5:33-54. on ammonites, inoceramids, and radiometric ages. United States Schwimmer, D.R., Stewart, J.D. and Williams, G.D. 1997. Scavenging by Geological Survey Open-File Report 2006-1250, 46 p. sharks of the Squalicorax in the Late Cretaceous of North Cumbaa, S.L., Schröder-Adams, C., Day, R.G. and Phillips, A.J. 2006. America. Palaios 12:71-83. Cenomanian bonebed faunas from the northeastern margin, Western Shimada, K. 2008. Ontogenetic parameters and life history strategies of Interior Seaway, Canada. Bulletin of New Museum of Natural the Late Cretaceous lamniform shark, Cretoxyrhina mantelli, based History and Science 35:139-155. on vertebral growth increments. Journal of Vertebrate Paleontology Cumbaa, S.L. Shimada, K. and Cook, T.D. 2010. Mid-Cretaceous vertebrate 28:21–33. faunas of the Western Interior Seaway of North America and their Shimada, K. and Martin, D.J. 2008. Fossil fishes from the basal Greenhorn evolutionary, paleobiogeographical, and paleoecological implications. Limestone (Upper Cretaceous: Late Cenomanian) in Russell County, Palaeogeography, Palaeoclimatology, Palaeoecology 195:199-214. Kansas. Fort Hays Studies (Special Issue Number 2), Fort Hays State Everhart, M.J. 2011. Occurrence of the hybodont shark genus University, Hays, Kansas, p. 89-103. Meristodonoides (; ) in the Shimada, K., Schumacher, B.A., Parkin, J.A. and Palermo, J.M. 2006. Fossil Cretaceous of Kansas. Kansas Academy of Science, Transactions marine vertebrates from the lowermost Greenhorn Limestone (Upper 114:33-46. Cretaceous: Middle Cenomanian) in southeastern Colorado. Journal of Gallardo, C., Shimada, K. and Schumacher, B.A. In press. A new Late Paleontology Memoir 63, 45 p. Cretaceous marine vertebrate assemblage from the basal Lincoln Shimada, K., Tsuihiji, T., Sato, T. and Hasegawa, Y. 2010. A remarkable Limestone Member of the Greenhorn Limestone in southeastern case of a shark-bitten elasmosaurid plesiosaur. Journal of Vertebrate Colorado. Kansas Academy of Science, Transactions. Paleontology 30:592-597. Gtandstaff, B.S. and Parris, D.C. 1990. Biostratigraphy of the fossil fish Underwood, C.J. and Cumbaa, S.L. 2010. Chondrichthyans from a Enchodus Agassiz. Journal of Vertebrate Paleontology 9(Suppl. 3):25A. Cenomanian (Late Cretaceous) bonebed, Saskatchewan, Canada. Hattin, D.E. 1965. Stratigraphy of the Graneros Shale (Upper Cretaceous) in Palaeontology 53:903-944. central Kansas. Kansas Geological Survey Bulletin 178, 83 p. Welles, S.P. 1970. The longest neck in the ocean. University of Nebraska Hattin, D.E. 1975. Stratigraphy and depositional environment of Greenhorn State Museum, Museum Notes 43:1-2. Limestone (Upper Cretaceous) of Kansas. Kansas Geological Survey Welton, B.J. and Farish, R.F. 1993. The Collector’s Guide to Fossil Sharks Bulletin 209, 128 p. and Rays from the Cretaceous of . Before Time, Lewisville, Texas, Hattin, D.E., Siemers, C.T. and Stewart, G.F. 1987. Upper Cretaceous 204 pp. stratigraphy and depositional environments of western Kansas. Kansas Witzke, B.J. 1981. Cretaceous vertebrate fossils of Iowa and nearby areas of Geological Survey Guidebook 3, 102 p. Nebraska, and . pp. 105-122 in Brenner, R.L., Jansen, K.R., Shimada, K. and Kirkland, K.I. In press. Fossil fish fauna Bretz, R.F., Bunker, B.J., Iles, D.L., Ludvigson, G.A., McKay, R.M., Whitley, from the uppermost Graneros Shale (Upper Cretaceous: middle D.L. and Witzke, B.J. (eds.), Cretaceous Stratigraphy and Sedimentation Cenomanian) in southeastern Nebraska. Kansas Academy of Science, in Northwest Iowa, Northeast Nebraska, and Southeast South Dakota. Transaction. Iowa Geological Survey Guidebook Series, Number 4

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