Niolamia

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Niolamia
Artistic reconstruction of life by Heinrich Harder 1914

Artistic reconstruction of life by Heinrich Harder 1914

Temporal occurrence
( Paleocene ?) Eocene
(66?) 56 to 33.9 million years
Locations
Systematics
Testudines
Halsberger tortoises (Cryptodira)
Eucryptodira
Meiolaniformes
Meiolaniidae
Niolamia
Scientific name
Niolamia
Ameghino , 1899
Skull of N. argentina in from above and from the side, after Woodward, 1901

Niolamia is a genus of tortoises in the group of the extinct Meiolaniidae from the Palaeogene of Patagonia (South America). The only known species of the monotypic genus is Niolamia argentina .

Etymology and history of research

The genus and type species were scientifically described and named for the first time by Florentino Ameghino in 1899 . The additional species “ argentina ” obviously refers to the locality in Patagonia. The meaning of the generic name Niolamia is unclear. It is probably a simple typo in the first description and it was actually meant " Miolania ", a synonym for Meiolania .

Strictly speaking, Ameghino's brief note does not meet the formal requirements of an initial paleozoological description . Apart from the presumably unsuccessful naming, precise and comprehensible information about the place of discovery is missing. The "Guaranitic Formation" in the area around the Río Sehuen and the Río Chubut is given as a find layer . A holotype is not mentioned , nor is an image attached. The anatomical analysis is limited to showing similarities with Meiolania platyceps and the brief mention of particularly pronounced processes in the skull area. Ameghino attributes the find to his brother Carlos.

A little later, in the same year 1899, Francisco P. Moreno , then director of the La Plata Museum (Museo de La Plata - MLP), publishes a brief description that apparently refers to the same fossil material. He assigns the find to an employee of his museum (Santiago Roth) and classifies it in the genus " Miolania " (= Meiolania ). Moreno adds a picture of the skull to his report, but neither does he provide a detailed description of diagnostic features.

The shortcomings in the early stages of Niolamia's research history are, at least in part, due to fierce competition between Ameghino and Moreno's research groups. The conflict among Argentine palaeontologists at the end of the 19th century was on a par with the much better known “ Bone Wars ” of their North American colleagues Marsh and Cope , a few years earlier.

It was not until two years later, in 1901, that Arthur Smith Woodward provided a first, more detailed description and corresponding illustrations of the Argentine finds (a skull, a lower jaw, both shoulder blades , parts of the carapace and a tail ring). Woodward uses the designation " Miolania argentina " and refers to Ameghino, 1899. However, he attributes the finds, in the sense of Moreno, to Santiago Roth. As a find layer he gives "... a widespread formation of red sandstones [in northern Patagonia], presumably dating back to the Cretaceous ..." ( Woodward, 1901 :).

In 1938, George Gaylord Simpson first describes the also horned turtle " Crossochelys corniger " from the Eocene Casamayor Formation in the province of Chubut and in this context reassesses the fossil material described by Woodward in 1901. Simpson calls the taxon again in the Ameghinos sense as Niolamia argentina and for the first time assigns it the skull described by Woodward in 1901 at the La Plata Museum (MLP 26-40) as a neotype . Furthermore, he shows that the "Guaranitic Formation" propagated by Ameghino does not consist exclusively of sediments from the Upper Cretaceous, but also from deposits of the Paleogene ; including the Casamayor formation (today Sarmiento formation) from which his " Crossochelys corniger " comes. Simpson reveals further inconsistencies in Ameghino's report and comes to the conclusion that it is no longer possible to understand whether Niolamia comes from the Cretaceous or from the Paleogene or even from both systems .

Only a complete reworking of the existing fossil material by Juliana Sterli and Marcelo S. de la Fuente in 2011 provided some clarity. This analysis produced two surprising results:

  • In the nasal cavity of the neotype , remnants of the rock from the original find layer could still be recovered and identified as whitish tuff . Such rocks are not present in the Cretaceous red sandstones of the area, as suggested by Woodward in 1901, but are widespread in the overlying Paleogenic sediments.
  • A closer comparison with the fossil material from " Crossochelys corniger " shows that there are no differences that cannot be interpreted as differences on an individual level. Sterli & de la Fuente, 2011 interpret “ Crossochelys corniger ” as con-specific (identical) to Niolamia argentina . The taxon " Crossochelys corniger " should be regarded as a younger synonym.

Subsequently, Sterli & de la Fuente, 2013, based on the work of Simpson, 1938 and Gaffney, 1996 develop a system for differentiating individual representatives of the Meiolaniformes based on the shape, size and distribution of the ossified horny scales ( "Scuta" ) in the skull area. A detailed summary of the current state of research is provided by Sterli, 2015.

In 2017 Paulina-Carabajal et al. the results of CT scans on the skulls of several members of the Meiolaniidae , including the neotype of N. argentina .

features

(After Sterli, 2015) Niolamia shows, with the exception of the typical tail lobe, all characteristics of a representative of the Meiolaniidae :

Characteristics at the generic level

The carapace of Niolamia is only preserved very fragmentarily, but can be estimated to be around 1.2 m long. Niolamia had thorn-like appendages and spines on its head, tail and carapace , which were probably used to ward off enemies. There were two large horns on the head. Above all, the ossified horn scales on the skull can be used to distinguish Niolamia from related forms (for easier understanding, the corresponding designations are, as far as possible, given in brackets in the illustration above according to Woodward, 1901):

  • The "A-scale" ("occ.") Is significantly enlarged and serves to protect the neck
  • The approximately rectangular (diamond-shaped in the related forms) "X-scale" ("II") is in contact with the "A-scale" (in other representatives of the Meiolaniidae , this scale is from the "D-scale" ("III") ) and surround the "G scale" and does not touch the "A scale")
  • The paired "D-scales" ("III") are completely separated from the "X-scale" ("II") and do not touch at the center line
  • "H-scales" are not available
  • The "D-scales" ("III") are accordingly in contact with the "F-scales" ("IV"); in other forms the “H-scales” lie in between
  • A large, laterally and backwards protruding extension on the "B-scale" ("I"); "Bb Horn"

Other generic characteristics are mentioned:

  • The friction surface between the toothless upper and lower jaw is simply structured, with only one labial (lip-side) and one lingual (tongue-side) back
  • The outer nostril is undivided
  • A nasomaxillary sinus, a pair of bulges in the anterior chamber as in Meiolania platyceps , is missing
  • Posterolateral (laterally posterior) spines on the outer edge of the carapace
  • Supracaudal shield present
  • A wide indentation in the area of ​​the pygale

Habitat and way of life

Niolamia probably lived a purely terrestrial way of life. However, since there is no information about the shape of the limbs, especially the forelimbs, this assumption is based purely on comparisons with the more fully known genus Meiolania . The greatly enlarged nasal cavity and the clearly set nasal vestibule of the genus are similar to those of some of today's aquatic turtles with snorkel-like noses, but can also be interpreted as an adaptation to life in arid desert areas. No reliable information can be given about the diet.

Individual evidence

  1. ^ A b c d A. Smith Woodward: On some extinct reptiles from Patagonia of the genera Miolania, Dinilysia, and Genyodectes. In: Proceedings of the Zoological Society of London , Vol. 70, Issue 1, pp. 169-184, 1901. (digitized version )
  2. ↑ a b c d J. Sterli & MS de la Fuente: Re-Description and Evolutionary Remarks on the Patagonian Horned Turtle Niolamia argentina Ameghino, 1899 (Testudinata, Meiolaniidae). In: Journal of Vertebrate Paleontology. Vol. 31, N0. 6, pp. 1210–1229, 2011. (digitized version )
  3. ↑ a b c d e f J. Sterli: A Review of the Fossil Record of Gondwanan Turtles of the Clade Meiolaniformes. In: Bulletin of the Peabody Museum of Natural History , Vol. 56, No. 1, pp. 21–45, 2015. (online)
  4. ↑ F. Ameghino: Sinopsis geológico-paleontológica. Suplemento (adiciones y correcciones). In: La Plata: Censo Nacional. 13 pp., 1899.
  5. ^ FP Moreno: Note on the discovery of Miolania and of Glossotherium (Neomylodon) in Patagonia. In: Geological Magazine , Vol. 6, No. 9, pp. 385–388, 1899. (digitized version)
  6. ↑ a b G. G. Simpson: Crossochelys, Eocene horned turtle from Patagonia. In: Bulletin of the American Museum of Natural History , Vol. LXXIV, Art. V, pp. 221-254, 1938. (digitized version )
  7. ↑ ES Gaffney: The postcranial morphology of Meiolania platyceps and a review of the Meiolaniidae. In: Bulletin of the American Museum of Natural History , No. 229, 165 S., 1996. (online)
  8. ^ A b J. Sterli & MS de la Fuente: New evidence from the Palaeocene of Patagonia (Argentina) on the evolution and palaeo-biogeography of Meiolaniformes (Testudinata, new taxon name). In: Journal of Systematic Palaeontology , Vol. 11, Issue 7, pp. 835–852, 2013. (digitized version )
  9. ↑ a b A. Paulina-Carabajal, J. Sterli, J. Georgi, SF Poropat & BP Kear: Comparative neuroanatomy of extinct horned turtles (Meiolaniidae) and extant terrestrial turtles (Testudinidae), with comments on the palaeobiological implications of selected endocranial features . In: Zoological Journal of the Linnean Society , Vol. XX, pp. 1–21, 2017. (digitized version)

Web links

Commons : Niolamia  - collection of images, videos and audio files