Placerias
{{Short description|Extinct genus of dicynodonts}}
{{speciesbox
| fossil_range = Late Carnian to Norian
~{{fossil range|230|215}}{{Cite journal |last1=Kent |first1=Dennis V. |last2=Olsen |first2=Paul E. |last3=Lepre |first3=Christopher |last4=Rasmussen |first4=Cornelia |last5=Mundil |first5=Roland |last6=Gehrels |first6=George E. |last7=Giesler |first7=Dominique |last8=Irmis |first8=Randall B. |last9=Geissman |first9=John W. |last10=Parker |first10=William G. |title=Magnetochronology of the Entire Chinle Formation (Norian Age) in a Scientific Drill Core From Petrified Forest National Park (Arizona, USA) and Implications for Regional and Global Correlations in the Late Triassic |url=https://geology.rutgers.edu/images/Kent20191.pdf |journal=Geochemistry, Geophysics, Geosystems |publisher=American Geophysical Union |publication-date=October 16, 2019 |volume=20 |issue=11 |pages=4654–4664 |doi=10.1029/2019GC008474|bibcode=2019GGG....20.4654K |s2cid=207980627 }}
| image = Placerias.jpg
| image_upright = 1.15
| image_caption = Skeleton
| parent_authority = Lucas, 1904
| taxon = Placerias hesternus
| authority = Lucas, 1904
}}
Placerias (meaning 'broad body'){{cite web|url=http://www.paleofile.com/Demo/Taxa/Placerias.htm|title=Page on Placerias|last=Paleofile|access-date=20 February 2010}} is an extinct genus of dicynodonts that lived during the Carnian to the Norian age of the Triassic Period (230–215 million years ago). Placerias belongs to a group of dicynodonts called Kannemeyeriiformes, which was the last known group of dicynodonts before the taxon became extinct at the end of the Triassic.
Description
Placerias was one of the largest herbivores in the Late Triassic, weighing up to {{convert|800|-|1000|kg|lb}}.{{Cite journal |last1=Hartman |first1=Scott A. |last2=Lovelace |first2=David M. |last3=Linzmeier |first3=Benjamin J. |last4=Mathewson |first4=Paul D. |last5=Porter |first5=Warren P. |date=November 2022 |title=Mechanistic Thermal Modeling of Late Triassic Terrestrial Amniotes Predicts Biogeographic Distribution |journal=Diversity |language=en |volume=14 |issue=11 |pages=973 |doi=10.3390/d14110973 |issn=1424-2818|doi-access=free }}{{Cite journal|last1=Fiorillo|first1=Anthony R.|last2=Padian|first2=Kevin|last3=Musikasinthorn|first3=Chayanin|date=2000|title=Taphonomy and Depositional Setting of the Placerias Quarry (Chinle Formation: Late Triassic, Arizona)|url=https://www.jstor.org/stable/3515510|journal=PALAIOS|volume=15|issue=5|pages=373–386|doi=10.2307/3515510|jstor=3515510 |issn=0883-1351|url-access=subscription}} The largest skull found had a length of {{convert|68|cm|in|1}}.{{Cite journal |last1=Green |first1=Jeremy |last2=Schneider |first2=Vince |last3=Schweitzer |first3=Mary |last4=Clarke |first4=Julia |date=2005-09-07 |title=NEW EVIDENCE FOR NON-PLACERIAS DICYNODONTS IN THE LATE TRIASSIC (CARNIAN-NORIAN) OF NORTH AMERICA |url=https://www.researchgate.net/publication/296314713 |journal=Journal of Vertebrate Paleontology |volume=25 |pages=65A–66A}}
Placerias had a powerful neck, strong legs, and barrel-shaped body with possible ecological and evolutionary parallels with the modern hippopotamus, spending much of its time during the wet season wallowing in the water and chewing at bankside vegetation. Placerias was closely related to Ischigualastia and similar in appearance.{{cite journal |last1=Vega-Dias |first1=Cristina |last2=Maisch |first2=Michael W. |last3=Schultz |first3=Cesar Leandro |title=A new phylogenetic analysis of Triassic dicynodonts (Therapsida) and the systematic position of Jachaleria candelariensis from the Upper Triassic of Brazil |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |date=2 March 2004 |volume=231 |issue=2 |pages=145–166 |doi=10.1127/njgpa/231/2004/145 |url=https://www.schweizerbart.de/papers/njgpa/detail/231/90103/A_new_phyologenetic_analysis_of_Triassic_dicynodon |archive-url=https://web.archive.org/web/20230521073426/https://www.schweizerbart.de/papers/njgpa/detail/231/90103/A_new_phyologenetic_analysis_of_Triassic_dicynodon |archive-date=21 May 2023 |url-access=subscription }} Placerias used its beak to slice through thick branches and roots with two short tusks that could be used for defence and for intra-specific display. The genus exhibits two morphs, one with short tusks and one with long tusks, which is inferred to be sexual dimorphism, with the longer-tusked individuals presumably being males.
Discovery
Fossils of forty Placerias were found near St. Johns, southeast of the Petrified Forest in the Chinle Formation of Arizona. This site has become known as the 'Placerias Quarry' and was discovered in 1930, by Charles Camp and Samuel Welles, of the University of California, Berkeley. Sedimentological features of the site indicate a low-energy depositional environment, possibly flood-plain or overbank. Bones are associated mostly with mudstones and a layer that contains numerous carbonate nodules. It is also known from the Pekin Formation of North Carolina.{{Cite web|url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=155546|title=Fossilworks: Placerias hesternus|website=fossilworks.org|access-date=17 December 2021}}
File:Postosuchus, Coelophysis, and Placerias.jpg (lower left) and Postosuchus (top left)]]
Placerias was originally considered the last of the dicynodonts, although other Late Triassic dicynodonts, such as Lisowicia{{Cite journal |last1=Racki |first1=Grzegorz |last2=Lucas |first2=Spencer G. |date=2020-04-20 |title=Timing of dicynodont extinction in light of an unusual Late Triassic Polish fauna and Cuvier's approach to extinction |url=https://doi.org/10.1080/08912963.2018.1499734 |journal=Historical Biology |volume=32 |issue=4 |pages=452–461 |doi=10.1080/08912963.2018.1499734 |bibcode=2020HBio...32..452R |s2cid=91926999 |issn=0891-2963|url-access=subscription }} and Pentasaurus have since been discovered.{{efn|A report of a dicynodont fossil from the Cretaceous Period{{cite journal| last1=Thulborn |first1=T. |last2= Turner |first2= S. |date=2003 |title=The last dicynodont: an Australian Cretaceous relic |journal= Proceedings of the Royal Society of London B |volume=270 |issue=1518 |pages= 985–993 |doi=10.1098/rspb.2002.2296 |pmid=12803915 |pmc=1691326}} proved to be neither Cretaceous nor a dicynodont; it proved to be a specimen of a diprotodontid marsupial that probably dates to the Pliocene or Pleistocene.{{cite journal |last1=Knutsen |first1=Espen M. |last2=Oerlemans |first2=Emma |title=The last dicynodont? Re-assessing the taxonomic and temporal relationships of a contentious Australian fossil |journal=Gondwana Research |date=January 2020 |volume=77 |pages=184–203 |doi=10.1016/j.gr.2019.07.011 |bibcode=2020GondR..77..184K |s2cid=202908716 }}}}
See also
Footnotes
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References
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External links
- [http://www.abc.net.au/dinosaurs/fact_files/dried/placerias.htm Walking with Dinosaurs – Fact File: Placerias]
- [http://www.enchantedlearning.com/subjects/dinosaurs/glossary/other/Placerias.shtml Dinosaur and Paleontology Dictionary: Placerias]
- [http://www.bbc.co.uk/sn/prehistoric_life/tv_radio/wwdinosaurs/ Walking with Dinosaurs website]
{{Anomodontia|K.}}
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{{Portal bar|Paleontology}}
Category:Carnian genus first appearances
Category:Late Triassic synapsids of North America
Category:Fossils of the United States
Category:Fossil taxa described in 1904
Category:Taxa named by Frederic Augustus Lucas