Pectodens: Difference between revisions
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==Discovery and naming== |
==Discovery and naming== |
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''Pectodens'' is known from one specimen, consisting of a well-preserved and almost complete skeleton. The fossil is preserved on two separate blocks that broke cleanly, but details of the [[pelvis]] were lost in the process. Additionally, the left femur is missing, as is part of one cervical. The specimen is catalogued as IVPP V18578, being stored in the [[Institute of Vertebrate Paleontology and Paleoanthropology]] in [[Beijing]], [[China]]. It was described by Chun Li, Nicholas Fraser, |
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Olivier Rieppel, Li-Jun Zhao, and Li-Ting Wang in a [[2017 in paleontology|2017]] research paper published in the [[Journal of Paleontology]].<ref name="desc"/> |
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The specimen itself was found in Luoping County in [[Yunnan]], [[China]]. It is part of the "Panxian-Luoping fauna", a [[faunal assemblage]] which is part of Member II of the [[Anisian]] ([[Middle Triassic]]) [[Guanling Formation]]. [[Conodont]] [[biostratigraphy]] (based on the presence of ''[[Nicoraella|Nicoraella kockeli]]'')<ref name="luoconodont">{{cite journal | last1 = Zhang | first1 = Q.-Y. | last2 = Zhou | first2 = C.-Y. | last3 = Lu | first3 = T. | last4 = Xie | first4 = T. | last5 = Lou | first5 = X.-Y. | last6 = Liu | first6 = W. | last7 = Sun | first7 = Y.-Y. | last8 = Huang | first8 = J.-Y. | last9 = Zhao | first9 = L.-S. | title = A conodont-based Middle Triassic age assignment for the Luoping Biota of Yunnan, China | journal = Science in China Series D: Earth Sciences | year = 2009 | volume = 52 | pages = 1673-1678 | url = https://link.springer.com/article/10.1007/s11430-009-0114-z}}</ref> and preliminary [[radiometric dating]]<ref name=liu2017>{{Cite journal|last=Liu|first=J.|last2=Organ|first2=C.L.|last3=Benton|first3=M.J.|last4=Brandley|first4=M.C.|last5=Aitchison|first5=J.C.|date=2017|title=Live birth in an archosauromorph reptile|url=http://www.nature.com/articles/ncomms14445|journal=Nature Communications|language=en|volume=8|doi=10.1038/ncomms14445|issn=2041-1723}}</ref> have dated the assemblage in Luoping to 244 million years old. Predominant deposits in Member II of the Guanling Formation consist of grey layers of [[marl]]y [[limestone]] and limestone.<ref name="desc"/><ref name="loc">{{cite journal | last1 = Benton | first1 = M.J. | last2 = Zhang | first2 = Q. | last3 = Hu | first3 = S. | last4 = Chen | first4 = Z.-Q. | last5 = Wen | first5 = W. | last6 = Liu | first6 = J. | last7 = Zhou | first7 = C. | last8 = Xie | first8 = T. | last9 = Tong | first9 = J. | last10 = Choo | first10 = B. | title = Exceptional vertebrate biotas from the Triassic of China, and the expansion of marine ecosystems after the Permo-Triassic mass extinction | journal = Earth-Science Reviews | volume = 123 | date = 2013 | pages = 199-243 | doi = 10.1016/j.earscirev.2013.05.014 | url = http://www.sciencedirect.com/science/article/pii/S0012825213001128}}</ref> |
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In their 2017 description of IVPP V18578, Li and colleagues named the new genus ''Pectodens'', from Latin ''pecto-'' ("comb") and ''dens'' ("tooth"), in reference to the animal's characteristic comb-like arrangement of elongated teeth. They also named the [[type species]] ''Pectodens zhenyuensis'' after Zhenyu Li, who had assisted with the collection of the specimen.<ref name="desc"/> |
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==Classification== |
==Classification== |
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Revision as of 05:41, 18 October 2017
| Pectodens Temporal range: Anisian,
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|---|---|
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Family: | †Trachelosauridae |
| Genus: | †Pectodens Li et al., 2017 |
| Type species | |
| Pectodens zhenyuensis Li et al., 2017
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Pectodens is an extinct genus of archosauromorph reptile which lived during the Middle Triassic in China. The type and only species of the genus is P. zhenyuensis, named by Chun Li and colleagues in 2017.
Description
Pectodens is a small animal with a slender build, measuring roughly 38 centimetres (15 in) long. The skull measures 25.7 mm (1.01 in) long, while the lower jaw was probably 25–26 mm (0.98–1.02 in) long when complete. Uniquely, numerous conical teeth in the jaws of Pectodens form a comb-like structure. These teeth have weakly-developed broad enamel ridges. There are 10 teeth in each premaxilla at the front of the jaw, and at least 24 more on the maxilla further back. There are also teeth on the palate, with at least 15 being present on the pterygoid bone. Additionally, the eye socket is very large, measuring 10.5 mm (0.41 in) long, although this may be due to the animal's immaturity. Meanwhile, the rear (temporal) region of the skull is quite short.[1]
The neck and tail of Pectodens were long, with the former being the same length as the torso. In life, it had 66 to 68 vertebrae, with 11-12 cervical vertebrae, 11-13 dorsal vertebrae, 2 sacral vertebrae, and 41 caudal vertebrae in the tail. The cervicals have low neural spines, like Tanystropheus. The cervical ribs are generally also long, having short forward processes and long rear processes that bridge two to three vertebral joints each. Meanwhile, the transverse processes of the dorsals are characteristically long and pronounced, terminating in sub-circular facet joints for the rounded heads of the ribs. Also like Tanystropheus, the transverse processes of the tail become gradually reduced alongside the forward processes of the chevrons, disappearing by the 35th caudal vertebra.[1]
Like Tanystropheus and Macrocnemus, the scapula is low. The long bones of the forelimbs have expanded and robust top ends; the deltopectoral crest on the humerus is also rather prominent. The humerus is longer than the ulna and radius, while the tibia and fibula are conversely slightly longer than the femur. An empty gap in the wrist suggests that not all of the wrist bones were ossified; the distal tarsals also appear to be missing from the ankle, but the remaining bones articulate directly with the foot. Unusually, there is no "hook" on the fifth metatarsal bone, unlike Tanystropheus. The hands and feet each have five digits, with the five digits respectively having 2, 3, 4, 5, and 4 phalanges (although there may only be 3 in the fifth digits of the hands).[1]
Discovery and naming
Pectodens is known from one specimen, consisting of a well-preserved and almost complete skeleton. The fossil is preserved on two separate blocks that broke cleanly, but details of the pelvis were lost in the process. Additionally, the left femur is missing, as is part of one cervical. The specimen is catalogued as IVPP V18578, being stored in the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. It was described by Chun Li, Nicholas Fraser, Olivier Rieppel, Li-Jun Zhao, and Li-Ting Wang in a 2017 research paper published in the Journal of Paleontology.[1]
The specimen itself was found in Luoping County in Yunnan, China. It is part of the "Panxian-Luoping fauna", a faunal assemblage which is part of Member II of the Anisian (Middle Triassic) Guanling Formation. Conodont biostratigraphy (based on the presence of Nicoraella kockeli)[2] and preliminary radiometric dating[3] have dated the assemblage in Luoping to 244 million years old. Predominant deposits in Member II of the Guanling Formation consist of grey layers of marly limestone and limestone.[1][4]
In their 2017 description of IVPP V18578, Li and colleagues named the new genus Pectodens, from Latin pecto- ("comb") and dens ("tooth"), in reference to the animal's characteristic comb-like arrangement of elongated teeth. They also named the type species Pectodens zhenyuensis after Zhenyu Li, who had assisted with the collection of the specimen.[1]
Classification
Paleobiology
Judging by the slender limbs and claw-tipped digits, Pectodens was an entirely terrestrial animal. It exhibits no adaptations for an aquatic lifestyle, unlike other archosauromorphs in its environment (the amphibious Qianosuchus, for instance, or the marine Dinocephalosaurus).[1]
Paleoecology
References
- ^ a b c d e f g Li, C.; Fraser, N.C.; Rieppel, O.; Zhao, L.-J.; Wang, L.-T. (2017). "A new diapsid from the Middle Triassic of southern China" (PDF). Journal of Paleontology. 91 (6): 1306–1312. doi:10.1017/jpa.2017.12.
- ^ Zhang, Q.-Y.; Zhou, C.-Y.; Lu, T.; Xie, T.; Lou, X.-Y.; Liu, W.; Sun, Y.-Y.; Huang, J.-Y.; Zhao, L.-S. (2009). "A conodont-based Middle Triassic age assignment for the Luoping Biota of Yunnan, China". Science in China Series D: Earth Sciences. 52: 1673–1678.
- ^ Liu, J.; Organ, C.L.; Benton, M.J.; Brandley, M.C.; Aitchison, J.C. (2017). "Live birth in an archosauromorph reptile". Nature Communications. 8. doi:10.1038/ncomms14445. ISSN 2041-1723.
- ^ Benton, M.J.; Zhang, Q.; Hu, S.; Chen, Z.-Q.; Wen, W.; Liu, J.; Zhou, C.; Xie, T.; Tong, J.; Choo, B. (2013). "Exceptional vertebrate biotas from the Triassic of China, and the expansion of marine ecosystems after the Permo-Triassic mass extinction". Earth-Science Reviews. 123: 199–243. doi:10.1016/j.earscirev.2013.05.014.