Dactylosaurus

Dactylosaurus
Temporal range: Lower and Middle Triassic (Olenekian to Anisian)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: †Sauropterygia
Order: †Nothosauroidea
Family: †Pachypleurosauridae
Genus: †Dactylosaurus
Gürich, 1884
Type species
†Dactylosaurus gracilis
Gürich, 1884
Synonyms

Dactylosaurus is a genus of nothosaur in the family Pachypleurosauridae. Along with Anarosaurus, Dactylosaurus was one of the earliest known pachypleurosaurs to come from Europe.[1]

Etymology

Dactylosaurus comes from the Greek daktulos (δακτυλος), "finger" and sauros (σαυρος), meaning "lizard" or "reptile."

Description

The nasal bones of Dactylosaurus meet and are broadly structured.[2] The upper temporal fenestra is large and kidney-shaped.[2] There are 17 cervical vertebrae[2] and the cervical ribs have anterior processes.[2] The maxillae of Dactylosaurus extended broadly up the side of the snout.[1]

D. gracilis

The holotype specimen (MGUWR WR 3871s) of D. gracilis was only a partial skeleton, consisting of the anterior end alone.[1] Because it differed slightly from the fossils of D. gracilis, it was first thought to belong to the species D. schroederi,[1] which is now considered a junior synonym for juvenile D. gracilis.[2] Once this was established, the juvenile fossil, which was found before the adult fossils, became the holotype. The one limb that was found (a left forelimb), was noted to have a slimmer radius and ulna than Neusticosaurus,[1] a similar nothosaur from Europe.[1] D. gracilis is the smallest known species in its family,[1] which includes the much more recognized Keichousaurus, a nothosaur often remembered for its small size.[3] The original holotype of D. gracilis is considered a juvenile,[2] however the size of a nothosaur when its bones harden is used to show size, making the estimate as smallest member of its family still valid.[1]

Distribution

Muschelkalk, a German form of shelly limestone, occasionally produces Dactylosaurus fossils in its lowest layers.

Dactylosaurus lived in the Lower and Middle Triassic period during the Late Olenekian and Anisian [2] faunal stage, of central Europe.[4]

In terms of geology, they are found: 1) in the uppermost Röt (uppermost Buntsandstein; Lower Triassic): e.g. Michałkowice (Siemianowice Śląskie) and Kamień Śląski, S Poland,[2] (the second location is not sure because Röt is not exposed there), 2) in the lowermost Muschelkalk (Middle Triassic), inter alia in the Gogolin Formation - Gogolin and its vicinity, S Poland.[4][5]

In 2012, the new Röt site (~ 247 Ma; Lower Triassic) with abundant disarticulated remains of Dactylosaurus was found in Gogolin.[6][7]

References

  1. 1 2 3 4 5 6 7 8 Lepidosauromorpha: Pachypleurosauridae: Dactylosaurus & Anarosaurus Palaeos.com. Last accessed 2008-07-04.
  2. 1 2 3 4 5 6 7 8 Rieppel, O & L Kebang (1995), "Pachypleurosaurs (Reptilia, Sauropterygia) from the Lower Muschelkalk, and a review of the Pachypleurosauroidea." Fieldiana Geol. N.S. 32: 1-44.
  3. ↑ "peripatus.gen.nz entry on Keichousaurus". Retrieved 2008-06-12.
  4. 1 2 "plesiosauria.com entry on Dactylosaurus". Retrieved 2008-06-13.
  5. ↑ Sues H-D., Carroll R.L. 1985. The pachypleurosaurid Dactylosaurus schroederi (Diapsida: Sauropterygia). Canadian Journal of Earth Sciences 22(11): 1602-1608
  6. ↑ Kowal-Linka M., Bodzioch A. 2012a. Warstwy kościonośne z Dactylosaurus (Reptilia, Sauropterygia) z retu (trias dolny, olenek) Opolszczyzny (Bonebeds with Dactylosaurus (Reptilia, Sauropterygia) from the Röt (Lower Triassic, Olenekian) in the Opole Silesia region (S Poland). Przegląd Geologiczny 60 (12): 646–649
  7. ↑ Kowal-Linka M., Bodzioch A. 2012b. New findings of vertebrate remains from the Röt (Lower Triassic, Olenekian) in the vicinity of Gogolin (Opole Silesia, S Poland). [W:] Krasiejów - inspiracje paleontologiczne / Krasiejów - paleontological inspirations. E. Jagt-Yazykova, J. Jagt, A. Bodzioch, D. Konietzko-Meier (red.). Zakład Poligraficzno-Wydawniczy "Plik", Bytom: 70-80. ISBN 978-83-916841-8-4
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