Daemonosaurus
| Daemonosaurus Temporal range:
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| Cast of the skull, displayed at the Ruth Hall Museum at Ghost Ranch | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Genus: | †Daemonosaurus Sueset al.2011 |
| Species: | †D. chauliodus
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| Binomial name | |
| †Daemonosaurus chauliodus Sueset al.2011
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Daemonosaurusis anextinctgenusof possibletheropoddinosaurfrom theLate TriassicofNew Mexico.The only known fossil is a skull and neck fragments from deposits of the latest TriassicChinle FormationatGhost Ranch.Daemonosauruswas an unusual dinosaur with a short skull and large, fang-like teeth. It lived alongside earlyneotheropodssuch asCoelophysis,which would have been among the most common dinosaurs by the end of the Triassic. However,Daemonosaurusretains severalplesiomorphic( "primitive" ) traits of the snout, and it likely lies outside thecladeNeotheropoda. It may be considered a late-survivingbasaltheropod or non-theropod basalsaurischian,possibly allied to other early predatory dinosaurs such asherrerasauridsorTawa.[1][2][3]
Discovery
[edit]
Daemonosaurusis known from a single fossil, theholotypeCM 76821, which consists of a skull, mandibles, anatlas bone,anaxis bone,otherneck vertebrae,and rib fragments. This specimen was discovered in a sediment block of collected from theCoelophysisQuarry (also known as the Whitaker quarry) atGhost Ranch,New Mexico.This site, preserving the informal lateNorianorRhaetian"siltstone member" of theChinle Formation,is famous for abundant fossils ofCoelophysis,an early theropod. C-4-81, the block containing CM 76821, was collected in the early 1980s byE.H. Colbertand is now housed in the collection of theCarnegie Museum of Natural HistoryinPittsburgh,Pennsylvania.Fossils ofCoelophysiswere also present in the block. CM 76821 was first uncovered by a volunteer preparing the block while it was on loan toState Museum of PennsylvaniainHarrisburg.[1][3]
Daemonosauruswas named byHans-Dieter Sues,Sterling J. Nesbitt,David S. Berman and Amy C. Henrici in the journalProceedings of the Royal Society Bin2011and thetype speciesisDaemonosaurus chauliodus.Thegeneric nameDaemonosaurusis derived from theGreekwords "daimon" (δαίμων) meaning "demon" and "sauros" (σαύρα) meaning "reptile". Thespecific nameis derived from the Greek word "chauliodous" (χαυλιόδους) meaning "prominent toothed", which is in reference to its procumbent front teeth.[1]
Description
[edit]Daemonosaurusis notable for its short, deep skull, with large teeth, a roundedorbit(eye socket) and a relatively smallantorbital fenestra.[1][2]Based on the proportions of relatedtheropods,Daemonosaurusis estimated to have been around 1.5 m (5 feet) long according to Sues.[3]An estimate byHoltz(2012) suggests thatDaemonosauruswas at most 2.2 m (7 ft) long with a weight around that of abeaver,9.1–22.7 kilograms (20–50 pounds).[4]These estimates are almost entirely conjectural, as no postcranial fossils are preserved beyond a few vertebrae. The proportionately large orbit, the short snout, and the apparent lack of fusion between the bones of the braincase suggest that theholotypespecimen CM 76821 may be a juvenile. On the other hand, the closure (fusion) of the neurocentral sutures in the vertebrae suggest a mature individual.[1]
Cranium
[edit]
Thepremaxillais deep and has a sloped front edge. The posterodorsal process (rear branch) of the premaxilla is broad and elongated, forming the entire rear edge of the relatively largenaris(nostril hole). The size of the posterodorsal process is more in line withHerrerasaurusandornithischiansthan with traditional theropods orsauropodomorphs.There are only three premaxillary teeth, likeTawa,Gnathovorax,Heterodontosaurus,and an unnamedBrazilianherrerasaurid,[5]but unlike other early dinosaurs, which have four. The premaxillary teeth are characteristically elongated, with the first tooth being the longest in the entire skull.[1][2]CT scansdemonstrate that this is a natural quality of the skull, as the teeth were not significantly displaced from their sockets.[2]The premaxillary teeth are straight at therootand curved at thecrown.All three are smooth on the front edge and finely serrated on the rear edge, and shallow grooves ornament the second and third teeth.[2]
Similar to many early dinosaurs, a smalldiastema(toothless notch) was present at the lower contact between the premaxilla andmaxilla.LikeTawaandHerrerasaurus,the outer surface of the maxilla is generally smooth and flat; there are no sharp ridges delimiting the tooth row or the shallow, upwards-orientedantorbital fossa.Nevertheless, there are a few pits on the outer surface, and a ridge-likepalatalprocess on the inner surface. The maxilla has 10 teeth at most, fewer than any other early dinosaur. While the recurved second and third maxillary teeth are nearly as long as the premaxillary teeth, the rest of the teeth gradually diminish in size and curvature towards the rear of the bone. On the other hand, serrations become more extensive on each tooth further down the tooth row.[1][2]
Thenasalis smooth and likely did not participate in the antorbital fossa. Each nasal has M-shaped sutures with the premaxilla andfrontal,a more complex configuration than in other early dinosaurs. Thelacrimalis thinnest at mid-height and sends a sharp projection along the lower edge of the orbit. It forms the rear edge of the antorbital fossa via a subtle ridge. Theprefrontalis proportionally large, forming about half the upper edge of the orbit. The size of the prefrontal is unique toDaemonosaurusamong dinosaurs and archosaurs in general. The frontals are wide and flat, separated from each other at the front by a wedge-shaped projection of the nasals. Their rear edge is excavated by thesupratemporal fossa,which extends onto the broad and mostly flatparietal,as well as the fairly largepostorbital.The postorbital likely contacted the frontal along a straight edge (likeTawaandHerrerasaurus), while also sending a rounded overhanging projection into the orbit (like most early saurischians).[1][2]
Thejugalis moderately deep, with a thick front prong. Likeneotheropodsand a few sauropodomorphs, the rear edge of the jugal bore a deep notch for the front of thequadratojugal.The jugal’s lower edge has a sharp ridge that projects straight down, an unusual configuration not seen in other dinosaurs. The quadratojugal is lightly-built, with narrow front and upper prongs similar toEoraptor.At its upper extent it contacts thesquamosal,a poorly-preserved bone with an overall boxy shape. Thequadrateis tall and narrow.[1][2]
Fragments of thepalateappear similar to other dinosaurs, with curvedectopterygoidsunderlapped by broadpterygoids.Thepalatinebone is large, sending out a diagonal lateral ridge to connect to the inner surface of the maxilla. Thebraincaseis partially disarticulated; eachotoccipital(outer rear segment of the braincase) sends out aparoccipital processwith parallel margins (like othersaurischians), while its base bears a pair of openings forcranial nerve XII.Unlike more advanced saurischians, theexoccipitalregion is flat, without a vertical lateral crest. Fragments of thebasioccipital,prootic,andparabasisphenoidare also preserved.Scleral ringswere present in each eye, with at least 11 ossicles overlapping in a counterclockwise pattern.[1][2]
Lower jaw
[edit]The front of themandible(lower jaw) has a slightly downturned tooth row, similar to many sauropodomorphs. Thesymphysis(chin) is dotted with small pits and converges towards a sharp margin. Thedentary(tooth-bearing portion of the jaw) has an estimated 10 teeth, which are curved and serrated. The first tooth is large and slightly inset from the tip of the jaw, the second tooth is the largest in the lower jaw, and the rest decrease in size to the back of the jaw. The rear of the jaw is poorly-preserved but appears to be similar in structure to that ofHerrerasaurus.[1][2]
Vertebrae
[edit]Fragments of fivecervical (neck) vertebraeare preserved alongside the skull. A slenderproatlaslinks the neck with the braincase. Theatlas(first cervical) has a thinneural archbearing a shallow depression followed byepipophyses,akin toHerrerasaurus.Epipophyses are also found in theaxis(second cervical), which is better preserved and has a slanted neural spine on top of a rectangularcentrum.The third cervical has prominentprezygapophysesand is unusual amongdinosauriformsin that it lacks a keel on its lower edge. A very large rimmed oval-shaped hole is present behind the rib articulations. This hole has been equated with pneumatic pockets ( “pleurocoels”) observed inTawa,Chindesaurus,and neotheropods.Cervical ribsare robust and have two closely set points of contact with the vertebrae. The fourth and fifth cervicals are fragmentary.[1][2]
Classification
[edit]Daemonosaurusis typically considered to be a basaltheropodthat lies outside the cladeNeotheropoda,a group that includes more advanced Triassic theropods (likeCoelophysis) and their descendants.[1]With such a basal position,Daemonosaurusrepresents a lineage that extended from the earliest radiation of dinosaurs in the Middle Triassic alongside forms such asEoraptorandHerrerasaurusfrom South America. Aphylogeneticanalysis conducted in its original description foundDaemonosaurus chauliodusto be closely related toTawa hallae,a theropod that was described from Ghost Ranch in 2009, and the Neotheropoda. Although the two theropods are closely related,Tawawas found at a quarry that is slightly older than the Whitaker Quarry at Ghost Ranch. Sueset al.(2011) noted that the discovery ofDaemonosaurusprovided "additional support for the theropod affinities of bothEoraptorandHerrerasauridaeand (demonstrated) that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. "Below is acladogrambased on the phylogenetic analysis conducted by Sueset al.in 2011, showing the relationships ofDaemonosaurus:[1]
Examination of this genus by Sueset al.(2011) demonstrates thatDaemonosaurusis separate and distinct from its other contemporaries.[1]Daemonosaurusdiffers fromHerrerasaurusbased on key features in the skull and because it has much larger teeth in thepremaxilla.Daemonosaurusdiffers fromEodromaeusbased on features of the jaw bone, skull, cheek bones, and because it has much larger teeth in the premaxilla.Daemonosaurusdiffers fromEoraptor lunensisbased on the presence of much larger premaxillary and anteriormaxillaryteeth and a much more restrictedantorbital fossaon the maxilla.Daemonosaurusdiffers fromTawa hallaeandCoelophysis bauriin features of the skull bones.Daemonosaurusdiffers fromChindesaurus bryansmalliin features of the cervical vertebrae.
A paper published by Baronet al.(2017) resurrected the cladeOrnithoscelidato uniteornithischiansand theropods to the exception ofsauropodomorphs.[6]Although not included in the original study, the authors addedDaemonosaurusto their dataset after their hypothesis was criticized by a team of international researchers, Langeret al.(2017).[7]In Baronet al.'s response,Daemonosauruswas found to be the earliest ornithischian, retaining many theropod-like characteristics.[8]
Nesbitt and Sues (2020) rescored the genus and reran the analyses of both Langeret al.(2017) and Baronet al.(2017). Langeret al.'s analysis resulted in a largepolytomyplacingDaemonosaurusas either a basal saurischian, a herrerasaurid, or a basalsilesaurid.WhenAgnosphitys(a fragmentary possible silesaurid) was removed from the analysis,Daemonosauruswas placed as the sister taxon toEusaurischia,which encompassed the theropod-sauropodomorph split. The rescoring of Baronet al.'s analysis placedDaemonosaurusas an ornithoscelidan outside the ornithichian-theropod split. This area was also occupied byTawaandChindesaurus.AlthoughDaemonosauruswas not recovered as an ornithichian in any analysis, it also does not share any clear unambiguous characteristics exclusively with theropods. Though Nesbitt and Sues (2020) consideredDaemonosaurusa likely saurischian, they were unable to conclusively place the genus within any subgroup of Dinosauria.[2]Novaset al.(2021) recoveredDaemonosaurusin a clade withTawaandChindesaurusthat is sister to Herrerasauridae, with this broaderHerrerasauriabeing a saurischian clade sister to Eusaurischia.[9]
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Paleoenvironment
[edit]The only specimen ofDaemonosauruswas recovered at theCoelophysis(Whitaker) quarry atGhost RanchinRio Arriba County,New Mexico.This site preserves pebbly, calcareous conglomerate rich in fossils of many different animals, with the theropod dinosaurCoelophysisbeing particularly abundant. It has been correlated the Siltstone Member of theChinle Formation,which is tentatively dated to theRhaetian(or possibly latestNorian) stage of the Late Triassic period.[1][2]
Ghost Ranch was located close to the equator 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation. Thepaleoenvironmentof the Whitaker quarry included a diverse collection of rhynchocephalians (likeWhitakersaurus),archosauromorphs,andarchosaurs.Archosauriform taxa present includephytosaurs(Redondasaurus),crocodylomorphs(Hesperosuchus),shuvosaurids(Effigia),thesilesauridEucoelophysis,and the dinosaurCoelophysis.[10]
Taphonomy
[edit]The multitude of specimens deposited so closely together atGhost Ranchwas probably the result of a flash flood event. Such flooding was commonplace during this period of theEarth's historyand, indeed, the nearbyPetrified ForestofArizonais the result of a preserved log jam of tree trunks that were caught in one such flood. In 1989, Colbert noted that theDaemonosaurusspecimen and severalCoelophysisspecimens were washed into a small pond, where they drowned and were buried by a sheet flood event from a nearby river. "[10]
References
[edit]- ^abcdefghijklmnopHans-Dieter Sues; Sterling J. Nesbitt; David S. Berman & Amy C. Henrici (2011)."A late-surviving basal theropod dinosaur from the latest Triassic of North America".Proceedings of the Royal Society B.278(1723): 3459–3464.doi:10.1098/rspb.2011.0410.PMC3177637.PMID21490016.
- ^abcdefghijklmnNesbitt, Sterling J.; Sues, Hans-Dieter (3 August 2020)."The osteology of the early-diverging dinosaurDaemonosaurus chauliodus(Archosauria: Dinosauria) from the Coelophysis Quarry (Triassic: Rhaetian) of New Mexico and its relationships to other early dinosaurs ".Zoological Journal of the Linnean Society.191:150–179.doi:10.1093/zoolinnean/zlaa080.
- ^abcChoi, C.Q. (12 April 2011)."T. Rex had a toothy ancestor that couldn't cut it".Live Science.Retrieved12 April2011.
- ^Holtz, Thomas R. Jr. (2012)Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,Winter 2011 Appendix.
- ^Garcia, Maurício S.; Müller, Rodrigo T.; Pretto, Flávio A.; Da-Rosa, Átila A. S.; Dias-Da-Silva, Sérgio (2021-01-02)."Taxonomic and phylogenetic reassessment of a large-bodied dinosaur from the earliest dinosaur-bearing beds (Carnian, Upper Triassic) from southern Brazil".Journal of Systematic Palaeontology.19(1): 1–37.doi:10.1080/14772019.2021.1873433.ISSN1477-2019.S2CID232313141.
- ^Baron, Matthew G.; Norman, David B.; Barrett, Paul (2017)."A new hypothesis of dinosaur relationships and early dinosaur evolution"(PDF).Nature.543(7646): 501–506.Bibcode:2017Natur.543..501B.doi:10.1038/nature21700.PMID28332513.S2CID205254710.
- ^Max C. Langer; Martín D. Ezcurra; Oliver W. M. Rauhut; Michael J. Benton; Fabien Knoll; Blair W. McPhee; Fernando E. Novas; Diego Pol; Stephen L. Brusatte (2017)."Untangling the dinosaur family tree"(PDF).Nature.551(7678): E1–E3.Bibcode:2017Natur.551E...1L.doi:10.1038/nature24011.hdl:1983/d088dae2-c7fa-4d41-9fa2-aeebbfcd2fa3.PMID29094688.S2CID205260354.
- ^Matthew G. Baron; David B. Norman; Paul M. Barrett (2017). "Baron et al. reply".Nature.551(7678): E4–E5.Bibcode:2017Natur.551E...4B.doi:10.1038/nature24012.PMID29094705.S2CID205260360.
- ^Novas, Fernando E.; Agnolin, Federico L.; Ezcurra, Martín D.; Temp Müller, Rodrigo; Martinelli, Agustín G.; Langer, Max C. (2021-10-01)."Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications".Journal of South American Earth Sciences.110:103341.Bibcode:2021JSAES.11003341N.doi:10.1016/j.jsames.2021.103341.ISSN0895-9811.
- ^abE. H. Colbert. 1989. The Triassic dinosaurCoelophysis.Museum of Northern Arizona Bulletin 57:1-174
