Caelestiventus

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Caelestiventus
Temporal range: Norian, 208 Ma
Caelestiventus skull.jpg
3D printed skull reconstruction; the dip in the forehead is perhaps too pronounced
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Order: Pterosauria
Family: Dimorphodontidae
Genus: Caelestiventus
Britt et al., 2018
Type species
Caelestiventus hanseni
Britt et al., 2018

Caelestiventus (meaning "heavenly wind") is a pterosaur genus from the Late Triassic (Norian or Rhaetian) found in western North America.[1] The type species, Caelestiventus hanseni, honors Robin Hansen, the Bureau of Land Management geologist (BLM), who facilitated access to the excavation site.

Caelestiventus is important because it is the sole example of a desert-dwelling non-pterodactyloid pterosaur and is 65 million years older than other known desert-dwelling pterosaurs. Additionally, it shows that the earliest pterosaurs were morphologically and ecologically diverse and that the Dimorphodontidae originated in the Triassic Period.[1]

Description

Most Triassic pterosaurs are small.[2][3][4] Caelestiventus, however, is one of, if not the largest known Triassic pterosaurs, with a wingspan of at least 1.5 metres (4 ft 11 in) and a skull 17.8 cm (7.0 in) long (based on a complete mandible).[1] Unlike most Triassic pterosaurs which are severely deformed by crushing, the bones of Caelestiventus are three-dimensional and uncrushed.[1] This preservation provides insights into the delicate structures of skull bones, including pneumatic features such as foramina/fossae and internal chambers.

Caelestiventus is known from a single individual (BYU 20707, in the Museum of Paleontology at Brigham Young University) that preserves much of the skull (skull cap, sides of the face, and a complete lower jaw (mandible) along with a single non-skull bone – the last finger bone at the end of the elongated fourth finger (manual digit IV 4) that supported the tip of the wing.[1]

Skull

Most of the skull is known. The laterally narrow and vertically deep skull is similar to that of Dimorphodon, with an enormous external naris (nostril) being the largest skull opening, and a large antorbital fenestra. Unlike most pterosaurs, the margin of the antorbital fenestra bears a remnant of an antorbital fossa.[1]

The skull roof has a median ridge as well as large ridges along the medial borders of the upper temporal fenestra that mark attachments for the muscle that closed the mandible. A prominent hood at the back of the skull, the nuchal crest, marks the attachment of large neck muscles. Sizeable pneumatic openings on the skull top lead into small pneumatic chambers in the skull roof. The uncrushed skull cap permitted the first endocranial reconstruction in a Triassic pterosaur and shows the brain had large cerebral lobes, from which the optic lobes bulge, and small olfactory lobes.[1]

The lower portion of the front of the mandible has a keel.[1] There are large pneumatic openings in the posterior mandible and the whole of the mandible is hollow and was likely air-filled (pneumatic).

Caelestiventus is heterodont, with three different tooth shapes - long fang-like spikes, large "leaf-shaped" blades, and tiny blades.[1]  There are two long, spike teeth near the front of each side of the lower jaws that were likely opposed by similar teeth at the tip of the skull snout (premaxilla). In the lower jaws, behind the fangs, is a tooth gap (diastema) which is followed by 38 tiny teeth on each side of the lower jaw (mandibular ramus). Each upper jaw bone (maxilla) is armed with twelve large, blade-like, triangular teeth. Both sides of the maxillary teeth are strengthened by a central ridge and these teeth terminate in two tips (bicuspid).

Discovery

Caelestiventus was recovered from the Saints & Sinners Quarry of northeastern Utah. The site was discovered in 2007 by Dan Chure and George Engelmann while working on the geology and paleontology of the fossilized dunes of the Nugget Sandstone.[5] In 2015, the find of a pterosaur skeleton was reported in the scientific literature.[6][7]

Classification

Phylogenetic analyses show Caelestiventus as the sister taxon to Dimorphodon macronyx in the family Dimorphodontidae, which was defined by Britt and colleagues as the most inclusive clade containing of Caelestiventus hanseni and Dimorphodon macronyx, the only two genera recovered as dimorphodontids in their analyses. They also found that the purported Dimorphodon species 'D.' weintraubi is the sister taxon to Anurognathidae, and thus was outside of Dimorphodontidae as defined by Britt and colleagues.[1]

Pterosauria

Austriadraco dallavecchiai

Arcticodactylus cromptonellus

Preondactylus buffarinii

Austriadactylus cristatus

Peteinosaurus zambellii

Macronychoptera
Dimorphodontidae

Dimorphodon macronyx

Caelestiventus hanseni

Lonchognatha
Eudimorphodontidae

Eudimorphodon ranzii

Carniadactylus rosenfeldi

Caviramus schesaplanensis

Raeticodactylus filisurensis

Novialoidea

Campylognathoides

Caelidracones
Anurognathidae

"Dimorphodon" weintraubi

Batrachognathus volans

Anurognathus ammoni

Dendrorhynchoides

Jeholopterus ningchengensis

Rhamphorhynchidae

Dorygnathus banthensis

Rhamphorhynchus muensteri

Scaphognathus crassirostris

Sordes pilosus

Monofenestrata

Darwinopterus

Pterodactylus antiquus

Pteranodon longiceps

Anhanguera

Paleoecology

Pterosaurs ranged from the Late Triassic to the end of the Cretaceous. The earliest known pterosaurs are from the late Triassic Period and provide insights into the origin and diversification of the group[3]. Triassic pterosaurs, however, are rare. In 2014, just twenty-seven specimens were reported to be known, many consisting of a single bone.[2][4] All but one, Arcticodactylus, come from the Alps.[2][3][4]

In addition to Caelestiventus, the Saints & Sinners Quarry has produced a diverse vertebrate fauna including two sphenosuchian genera, two sphenodontian genera, a drepanosaurid, a procolophonid and two theropod dinosaurs – a coelophysoid and a medium-sized genus represented only by teeth.[5] No invertebrates are known from the site. Plants from the quarry consist of Bennettitalean fronds.[1]

References

  1. ^ a b c d e f g h i j k Britt, B. B.; Dalla Vecchia, F. M.; Chure, D. J.; Engelmann, G. F.; Whiting, M. F.; Scheetz, R. D. (2018). "Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years". Nature Ecology & Evolution. doi:10.1038/s41559-018-0627-y. ISSN 2397-334X.
  2. ^ a b c Dalla Vecchia, F. M. (2014). Gli pterosauri triassici. Memorie del Museo Friulano di Storia Naturale. 54. Udine: Museo Friulano di Storia Natural. ISBN 9788888192543.
  3. ^ a b c Dalla Vecchia, F. M. (2013). "Triassic pterosaurs". In Nesbitt, S. J.; Desojo, J. B.; Irmis, R. B. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications. 379. pp. 119–155. doi:10.1144/SP379.14.
  4. ^ a b c Kellner, A. W. A. (2015). "Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa". Anais da Academia Brasileira de Ciências. 87 (2): 669–689. doi:10.1590/0001-3765201520150307. ISSN 0001-3765.
  5. ^ a b Britt, B. B.; Chure, D. J.; Engelmann, G. F.; Shumway, J. D. (2016). "Rise of the erg—Paleontology and paleoenvironments of the Triassic-Jurassic transition in Northeastern Utah". Geology of the Intermountain West. 3: 1–32. doi:10.31711/giw.v3i0.5. ISSN 2380-7601.
  6. ^ Britt, B.B., Chure, D.J., Engelmann, G.F., Dalla Vecchia, F., Scheetz, R., Meek, S., Thelin, C., and Chambers, M., 2015, "A new, large, non-pterodactyloid pterosaur from a Late Triassic interdunal desert environment within the eolian Nugget Sandstone of northeastern Utah, USA, indicates early pterosaurs were ecologically diverse and geographically widespread", Journal of Vertebrate Paleontology, Program with Abstracts, p. 97
  7. ^ Britt, B.B., Dalla Vecchia, F.M., Chure, D.J., Engelmann, G.F., Chambers, M.A, Thelin, C., Scheetz, R., 2015, "New Triassic pterosaur from interdunal desert deposits of the Nugget Sandstone NE Utah, USA", Flugsaurier 2015, 5th International Symposium on Pterosaurs, Portsmouth, England, Program with Abstracts, p. 17–18
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