Dactylosaurus

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]

Dactylosaurus
Temporal range: Early-Middle Triassic,
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: †Sauropterygia
Family: †Pachypleurosauridae
Genus: †Dactylosaurus
Gürich, 1884
Type species
†Dactylosaurus gracilis
Gürich, 1884
Synonyms

Etymology

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

Description

Dactylosaurus was a small reptile measuring up to 50 cm (1.6 ft) long.[2] The nasal bones of Dactylosaurus meet and are broadly structured.[3] The upper temporal fenestra is large and kidney-shaped.[3] There are 17 cervical vertebrae[3] and the cervical ribs have anterior processes.[3] 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.[3] 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.[4] The original holotype of D. gracilis is considered a juvenile,[3] 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 Early and Middle Triassic period during the Late Olenekian and Anisian[3] faunal stage, of central Europe.[5]

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,[3] (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.[5][6]

In 2012, the new Röt site (~ 247 Ma; Lower Triassic; the latest Olenekian) with abundant disarticulated remains of Dactylosaurus was found in Gogolin. Presently, this in the only site where Dactylosaurus remains are accessible to collect.[7][8][9]

References
  1. Lepidosauromorpha: Pachypleurosauridae: Dactylosaurus & Anarosaurus Archived 2008-06-24 at the Wayback Machine Palaeos.com. Last accessed 2008-07-04.
  2. Klein, N.; Griebeler, E.M. (2018). "Growth patterns, sexual dimorphism, and maturation modeled in Pachypleurosauria from Middle Triassic of central Europe (Diapsida: Sauropterygia)". Fossil Record. 21 (1): 137–157. doi:10.5194/fr-21-137-2018.
  3. 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.
  4. "peripatus.gen.nz entry on Keichousaurus". Archived from the original on 2008-04-29. Retrieved 2008-06-12.
  5. "plesiosauria.com entry on Dactylosaurus". Archived from the original on 2009-01-05. Retrieved 2008-06-13.
  6. Sues H-D., Carroll R.L. 1985. The pachypleurosaurid Dactylosaurus schroederi (Diapsida: Sauropterygia). Canadian Journal of Earth Sciences 22(11): 1602-1608
  7. 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
  8. 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
  9. Kowal-Linka M., Bodzioch A. 2017. Genesis of the Lower Triassic bonebeds from Gogolin (S Poland): The impact of microbial mats on trapping of vertebrate remains. Palaeogeography, Palaeoclimatology, Palaeoecology 466, 38–58
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