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Vrije Universiteit Brussel Multigenerational assemblage of Triceratops from the Newcastle area, Wyoming, USA - an in-depth analysis of cranial and post-cranial ontogenesis Bastiaans, Dylan; Trapman, Tom; Guliker, Martijn; Kaskes, Pim; Schulp, Anne S. Published in: Journal of Vertebrate Paleontology, Program and Abstracts, 2016 Publication date: 2016 Document Version: Final published version Link to publication Citation for published version (APA): Bastiaans, D., Trapman, T., Guliker, M., Kaskes, P., & Schulp, A. S. (2016). Multigenerational assemblage of Triceratops from the Newcastle area, Wyoming, USA - an in-depth analysis of cranial and post-cranial ontogenesis. In Journal of Vertebrate Paleontology, Program and Abstracts, 2016 (pp. 94-94) General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 10. Jul. 2020

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Page 1: MULTIGENERATIONAL ASSEMBLAGE OF TRICERATOPS FROM … · MULTIGENERATIONAL ASSEMBLAGE OF TRICERATOPS FROM THE NEWCASTLE AREA, WYOMING, USA – AN IN-DEPTH ANALYSIS OF CRANIAL AND POST-CRANIAL

Vrije Universiteit Brussel

Multigenerational assemblage of Triceratops from the Newcastle area, Wyoming, USA -an in-depth analysis of cranial and post-cranial ontogenesisBastiaans, Dylan; Trapman, Tom; Guliker, Martijn; Kaskes, Pim; Schulp, Anne S.

Published in:Journal of Vertebrate Paleontology, Program and Abstracts, 2016

Publication date:2016

Document Version:Final published version

Link to publication

Citation for published version (APA):Bastiaans, D., Trapman, T., Guliker, M., Kaskes, P., & Schulp, A. S. (2016). Multigenerational assemblage ofTriceratops from the Newcastle area, Wyoming, USA - an in-depth analysis of cranial and post-cranialontogenesis. In Journal of Vertebrate Paleontology, Program and Abstracts, 2016 (pp. 94-94)

General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.

• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal

Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.

Download date: 10. Jul. 2020

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Page 3: MULTIGENERATIONAL ASSEMBLAGE OF TRICERATOPS FROM … · MULTIGENERATIONAL ASSEMBLAGE OF TRICERATOPS FROM THE NEWCASTLE AREA, WYOMING, USA – AN IN-DEPTH ANALYSIS OF CRANIAL AND POST-CRANIAL

MULTIGENERATIONAL ASSEMBLAGE OF TRICERATOPS FROM THE NEWCASTLE AREA, WYOMING, USA –

AN IN-DEPTH ANALYSIS OF CRANIAL AND POST-CRANIAL ONTOGENESIS Dylan Bastiaans1,2*, Tom Trapman1,2, Martijn Guliker2, Pim Kaskes3, Anne Schulp2, 3

1Utrecht University, Faculty of Geosciences, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands; 2Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands;

3Vrije Universiteit, Department of Earth Sciences, De Boelelaan, 1081 HV Amsterdam, The Netherlands

Here we report on a multigenerational assemblage of Triceratops from the Upper Maastrichtian Lance Formation near Newcastle, eastern Wyoming, USA. While fieldwork is still ongoing, in excess of eight hundred elements have already been uncovered, belonging to a minimal number of six individuals. Detailed geological fieldwork at the excavation site shows that the Triceratops skeletons are entombed within an organic-rich clay to siltstone unit characterized by abundant micro- and macro-floral and -vertebrate remains. The Triceratops bones are associated, but also show clear disarticulation. The fifth skeleton is located at the same site, but circa 4 meters above the main bonebed. The site is remarkable since it yields both cranial and post-cranial remains of individuals of different sizes, representing several ontogenetic stages. This assemblage is one of only a handful known sites of the genus Triceratops that contain abundant post-cranial material4,6. Ontogeny and especially the validity of taxa in Triceratops, and other Chasmosaurinae (e.g. Torosaurus), have been heavily debated subjects5,9. However, studies have mostly been restricted to descriptions of cranial material due to the scarcity of post-cranial remains1,2,3,9. Therefore, this assemblage helps to fill in a gap in our knowledge regarding the post-cranial development of these highly derived ceratopsids. This site offers a higher resolution in the ontogenetic development in particularly the late juvenile or early sub-adult to adult stages of Triceratops. By combining histology, allometric measurements, and analysis of morphological characters, the timing of attaining skeletal maturity along with the expression of morphological characters, like suture closure and cranial ornamentation, can be specified. It is evident that individuals in the sub-adult stage reach near-adult size before the closure of most cranial sutures. Additionally, it is recognized that certain post-cranial elements, especially in the pelvic region, experience major remodelling during ontogeny. Future studies with emphasis on intense histological sampling and the use of (µ-)CT scans, will aid in determining the specific timing of these ontogenetic changes.

Site B

Main “bonebed"

The Darnell site relative to the other two known monospecific assemblages of Triceratops4,6. The Darnell site is located in the Lance formation, near the town of Newcastle, WY (modified from: Fastovsky & Bercovici, 2016)

Two stratigraphic levels produced elements of multiple Triceratops: the main "bonebed" layer has yielded a MNI of 4; while site B (Triceratops "Dirk") positioned ca.4 m above the main "bonebed", represents a MNI of 2

Lithostratigraphy and sedimentology of the two Triceratops-bearing layers, indica-ting two different preservational settings. Laser-diffraction particle-size analysis provided grain-size class % and grain-size distribution data whereas thermogravi-metry offered total carbonate and organic weight % of the sediments. The main bonebed layer is characterized as a well-sorted clay to very fine silt deposit that is rich in organic matter. Site B is a less well-sorted, clay to very fine sand level which is more depleted in organic remains7

The bone distribution within the main Triceratops-bearing layer, possibly reflecting a marsh-like deposit (oxbow or floodplain marsh). The preliminary MNI is based upon the number of femora recovered (red).

The bone distribution of the presumed (early) subadult Triceratops ("Dirk") recovered from the overburden 4,5m above the main bone-bed layer, represen-ting "Site B". These remains show a semi-associated distribution pattern as op-posed to the disarticulated main bonebed layer.

References 1Goodwin, M.B. et al., 2006. The Smallest Known Triceratops Skull : New Observations On Ceratopsid Cranial Anatomy And Ontogeny. Journal of Vertebrate Paleontology, 26(March), pp.103–112. 2Hatcher, J.B., Marsh, O.C. & Lull, R.S., 1907. The Ceratopsia: Monograph 49. United States Geological Survey, pp.1–198. 3Horner, J.R. & Goodwin, M.B., 2006. Major cranial changes during Triceratops ontogeny. Proceedings. Biological sciences / The Royal Society, 273(1602), pp.2757–61. 4Keenan, S.W. & Scannella, J.B., 2014. Paleobiological implications of a Triceratops bonebed from the Hell Creek Formation , Garfield County, northeastern Montana. Geological Society of America Special Papers, (503), pp.349–364. 5Longrich, N.R. & Field, D.J., 2012. Torosaurus is not Triceratops: ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy. PloS one, 7(2), p.e32623. 6Mathews, J.C. et al., 2009. The first Triceratops bonebed and its implications for gregarious behavior. Journal of Vertebrate Paleontology, 29(1), pp.286–290. 7Portanger, L.A., 2016. Sedimentological analysis of the Darnell Triceratops Bonebed in eastern Wyoming, USA: reconstruction of the depositional environment and possible taphonomic scenarios. Unpublished BSc thesis. Vrije Universiteit, Amsterdam, pp.1–68. 8Scannella, J.B. & Horner, J.R., 2010. Torosaurus Marsh , 1891, is Triceratops Marsh , 1889 (Ceratopsidae : Chasmosaurinae): Synonymy Through Ontogeny. Journal of Vertebrate Paleontology, 1889(4), pp.1157–1168. 9cannella, J.B. et al., 2014. Evolutionary trends in Triceratops from the Hell Creek Formation, Montana. Proceedings of the National Academy of Sciences of the United States of America, 111(28), pp.10245–50.

Composite of the main "bonebed"

The heat map depicting the preservation potential of various skeletal elements. As would be expected, large robust elements show a higher preservation frequency than the smaller elements (i.e. comprising the manus and pes). This site, however, is unique in the relatively high preservation potential of terminal elements (e.g. phalanges, caudal vertebrae and isolated epoccipitals).

The bones of the Triceratops recovered from the upper layers, nicknamed “Dirk”, representing a presumed (early) subadult.

A variation of ontogenetic ages could readily be distinguished, ranging from (early) subadult to (late-stage) adult, as illustrated by for instance the cranial ornamentation, as well as distinct variation in overall size and bone surface textures (i.e. large scale remodeling)1,2,3,9.

Triceratops "Dirk"

* [email protected]

NEWCASTLE, WYOMING

Acknowledgements

First off, we owe many thanks to the team of volunteers and students for their efforts in recovering the remains of the abovementioned Triceratops during the field seasons of 2015 and 2016. Furthermore, additional thanks to Peter Larson and his crew of the Black Hills Institute of Geological Research for providing help and assistance in this. In addition, special thanks and acknowledgement to Nancy and Donley Darnell, for graciously allowing us to search and excavate on their land and for accepting us with open arms for hopefully years to come. Lastly, we would like to thank the Scholarship Supporting Neoceratopsian Research, by Darren Tanke, for the provided financial support that allowed us to present these preliminary results at the current annual meeting.

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