Azendohsauridae
| Azendohsauridae Temporal range:
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| Life restorationofShringasaurus indicus | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Clade: | †Allokotosauria |
| Family: | †Azendohsauridae Nesbittet al.,2015 |
| Subgroups | |
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Azendohsauridaeis afamilyofallokotosaurianarchosauromorphsthat lived during theMiddletoLate Triassicperiod, around 242-216 million years ago. The family was originally named solely for the eponymousAzendohsaurus,marking out its distinctiveness from other allokotosaurs,[1]but as of 2022[update]the family now includes four othergenera:thebasalgenusPamelaria,the large horned herbivoreShringasaurus,[2]and two carnivorous genera grouped into thesubfamily-level subcladeMalerisaurinae,MalerisaurusandPuercosuchus,and potentially also thedubiousgenusOtischalkia.[3][4]Most fossils of azendohsaurids have aGondwanandistribution, with multiple species known acrossMoroccoandMadagascarinAfricaas well asIndia,although fossils of malerisaurine azendohsaurids have also been found in the southwesternUnited StatesofNorth America.
Azendohsaurids are notable for the various dinosaur-like traits found in some species, including thesauropodomorph-like neck, jaws and teeth ofAzendohsaurus,theceratopsid-like horns ofShringasaurus,andtheropod-like teeth ofPuercosuchus.[1][2][4]These traits are allconvergently evolvedwith later dinosaurs, and some similarities are so striking that it is difficult to distinguish isolated azendohsaurid teeth and jaw bones from those of dinosaurs. Indeed,Azendohsaurusitself was initially described as a herbivorous dinosaur until better remains of its skull and skeleton were found.[5]
Description
[edit]Azendohsaurids were robust quadrupeds with sprawled limbs, characterised by their long necks and proportionately small heads, and reached body sizes of up to 3 or 4 metres (9.8 or 13.1 ft) in length in the largest species.[2]Although initially characterised as herbivores based solely onAzendohsaurus,azendohsaurids had a diverse diet and lifestyles including large herbivores, insectivores, and carnivores. Consequently, although broadly similar in body form, their skulls varied from short and boxy with leaf-shaped teeth, to long and narrow with recurved, blade-like teeth.[1][4][6]
Azendohsaurids lack a prenarial process, the bony splint of thepremaxillathat otherwise divides the twoexternal naresin typical reptile skulls, giving them a single fused (confluent) opening for their nostrils. Another characteristic of azendohsaurids is that they often possess palatal teeth on the roof of their mouths similar in size and shape to those along the jaw margins, including serrations, compared to the typical tiny and conical palatal teeth of other reptiles. Such large and specialised palatal teeth are known definitively inPamelaria,AzendohsaurusandShringasaurus,[7][8]while simpler but notably large palatal teeth with coarse serrations are found inMalerisaurus.[3]The palatal teeth ofPuercosuchus,however, are simply described as "peg-like".[4]
All known azendohsaurids have long necks, withneck vertebraevery similar in shape and construction to those of early sauropodomorph dinosaurs, and held them raised above their shoulders. Theshoulder girdlesthemselves are tall and very well developed, with longscapularblades. Azendohsaurids had a sprawling gait like other early archosauromorphs, although theirshoulder jointfaces back as well as out to the sides, suggesting they may have been able to hold their forelimbs closer to their body. Their bodies are deep, ranging from relatively narrow-bodied inPamelariato barrel-shaped inAzendohsaurus,and their tails are proportionally shorter and stockier compared to other archosauromorphs.[1][4][6]
Classification and evolution
[edit]Azendohsaurids are one of two or three families included in the clade Allokotosauria, a group of unusual Triassic non-archosaurarchosauromorphs that also includes the familiesTrilophosauridaeand possibly the glidingKuehneosauridae.[1][9]They have consistently been recognised as thesister taxonof trilophosaurids, initially united on shared yet differing herbivorous traits. However, as more azendohsaurids have been discovered and recognised, they demonstrate that the group was likely to be ancestrally carnivorous.[4]
Aphylogenetic analysisperformed by palaeontologist Sterling J. Nesbitt and colleagues in 2021 included all recognised azendohsaurids and other allokotosaurian taxa. Their results foundPamelariato be the earliest branching azendohsaurid, with the remaining azendohsaurids divided into two subclades, one containing the herbivoresShringasaurusand two species ofAzendohsaurus,and the Malerisaurinae containing both species ofMalerisaurusand similar larger material (including the material that would be namedPuercosuchus). Thecladogrambelow depicts the simplified consensus result of their analysis, where the uncertain relationships within Malerisaurinae are presented as apolytomy:[3]
| Allokotosauria | |
- ^Representing material referred to'Otischalkia elderae'and similar-sized material.[4]
- ^Taxon described asPuercosuchusin 2022.[4]
Biogeography
[edit]The oldest known azendohsaurids arePamelariaandShringasaurus,both from India and dated to theAnisianstageof theMiddle Triassic.Azendohsaurusitself has been dated from the end of the Middle Triassic during theLadinian(at least forA. madagaskarensis) into theCarnianstage of the earliestLate Triassicin Morocco and Madagascar.[8]Malerisaurines, includingMalerisaurusandPuercosuchus,are exclusively known from theLate Triassicduring an interval from the late Carnian into the earlyNorianof both India and North America, and are the latest-surviving azendohsaurids known. This is in spite of their relativelyplesiomorphic(i.e. ancestral) features compared to other azendohsaurids, representing arelictuallineage of early-diverging carnivorous azendohsaurids that survived longer than their more derived herbivorous kin. Malerisaurines disappear from the fossil record in North America at or the near the end of theAdamanianteilzone(a localbiostratigraphicunit in the southwestern United States) roughly 216 million years ago, marking the extinction of the azendohsaurids globally.[3][4]
References
[edit]- ^abcdeNesbitt, S.J.; Flynn, J.J.; Pritchard, A.C.; Parrish, M.J.; Ranivoharimanana, L.; Wyss, A.R. (2015)."Postcranial osteology ofAzendohsaurus madagaskarensis(?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles "(PDF).Bulletin of the American Museum of Natural History(398): 1–126.doi:10.5531/sd.sp.15.hdl:2246/6624.ISSN0003-0090.
- ^abcSengupta, Saradee; Ezcurra, Martín D.; Bandyopadhyay, Saswati (21 August 2017)."A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India".Scientific Reports.7(1): 8366.Bibcode:2017NatSR...7.8366S.doi:10.1038/s41598-017-08658-8.PMC5567049.PMID28827583.
- ^abcdNesbitt, S. J.; Stocker, M. R.; Ezcurra, M. D.; Fraser, M. C.; Heckert, A. B.; Parker, W. G.; Mueller, B.; Sengupta, S.; Bandyopadhyay, S.; Pritchard, A. C.; Marsh, A. D. (2021)."Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India".Papers in Palaeontology.8.doi:10.1002/spp2.1413.S2CID245049571.
- ^abcdefghiMarsh, Adam D.; Parker, William G.; Nesbitt, Sterling J.; Kligman, Ben T.; Stocker, Michelle R. (2022)."Puercosuchus traverorum n. gen. n. sp.: a new malerisaurine azendohsaurid (Archosauromorpha: Allokotosauria) from two monodominant bonebeds in the Chinle Formation (Upper Triassic, Norian) of Arizona".Journal of Paleontology.96(S90): 1–39.Bibcode:2022JPal...96S...1M.doi:10.1017/jpa.2022.49.ISSN0022-3360.
- ^Flynn, J.J.; Nesbitt, S.J.; Parrish, J.M.; Ranivoharimanana, L.; Wyss, A.R. (2010)."A new species ofAzendohsaurus(Diapsida: Archosauromorpha) from the Triassic Isalo Group of southwestern Madagascar: cranium and mandible ".Palaeontology.53(3): 669–688.Bibcode:2010Palgy..53..669F.doi:10.1111/j.1475-4983.2010.00954.x.
- ^abSen, K. (2003). "Pamelaria dolichotrachela,a new prolacertid reptile from the Middle Triassic of India ".Journal of Asian Earth Sciences.21(6): 663–681.Bibcode:2003JAESc..21..663S.doi:10.1016/S1367-9120(02)00110-4.
- ^Martín D. Ezcurra (2016)."The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms".PeerJ.4:e1778.doi:10.7717/peerj.1778.PMC4860341.PMID27162705.
- ^abSengupta, S.; Bandyopadhyay, S. (2022). "The osteology ofShringasaurus indicus,an archosauromorph from the Middle Triassic Denwa Formation, Satpura Gondwana Basin, Central India ".Journal of Vertebrate Paleontology.41(5): e2010740.doi:10.1080/02724634.2021.2010740.S2CID247038160.
- ^Pritchard, Adam C.; Nesbitt, Sterling J. (2017-10-11)."A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida".Royal Society Open Science.4(10): 170499.Bibcode:2017RSOS....470499P.doi:10.1098/rsos.170499.ISSN2054-5703.PMC5666248.PMID29134065.
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