Wonambi

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Wonambi
Skeletal reconstructions of Wonambi naracoortensis and Thylacoleo carnifex

Skeletal reconstructions of Wonambi naracoortensis and Thylacoleo carnifex

Temporal occurrence
Lower Miocene to? Holocene
23.03 to 0.012 million years
Locations
Systematics
Scale reptiles (Squamata)
Toxicofera
Snakes (serpentes)
Madtsoiidae
Wonambi
Scientific name
Wonambi
Smith , 1976

Wonambi is a large genus of snakes from the late Cenozoic of Australia from the family Madtsoiidae, which is known only in fossil form.

etymology

The name "Wonambi" comes from an Aboriginal language and describes the mythical rainbow snake . It was coined in 1976 by the Australian paleontologist Meredith J. Smith .

features

Holotype of Wonambi naracoortensis , a single trunk vertebra, viewed from the left (schematic)
Elements and fragments of the upper jaw of Wonambi naracoortensis

The genus Wonambi or its type species Wonambi naracoortensis (see below) is, as is common for fossil snake species, primarily defined by the special features of their trunk vertebrae. These are high, back-upward (posterodorsal) directed spinous process with a sharp front edge ("pre-spinal lamina") almost to the edge of the zygosphere ; a relatively narrow zygosphere with steep articular surfaces inclined 20 to 30 ° from the vertical; large paradiapophyses I , which protrude laterally over the zygapophyses in most trunk vertebrae, with a concave upper (dorsal) edge of the diapophysis in side view; Relatively strongly inclined zygapophyses, inclined 20 ° or more to the horizontal, and a relatively weakly pronounced abdominal keel ( hemal keel ), which in the rear third of the vertebra is often characteristically formed as a double or triple keel . As a further diagnostic features of the genus will be named an approximately centrally running on the bone significantly (media) from the inner edge remote Pterygoidal row of teeth, a triangular in palate view of the outer (lateral) extension of the Pterygoids for articulation with the Ectopterygoid (engl. Ectopterygoid process ) , a narrow basipterygoid joint that points inwards (mediad) as well as upwards (dorsad) , a relatively elongated and flat maxillary and dentals and a deep, anterolateral-posteromedially oriented groove (probably the setting for the ventral edge of the jugal) on the dorsal side of the maxillary.

Wonambi was a very large snake. Calculations for a largely complete skeleton found in Naracoorte resulted in a live length of 5.4 to 6.1 m, which would have resulted in a live weight of up to 250 kg with a maximum body diameter of 25 cm and a maximum circumference of 80 cm. The very original structure of the skull is striking. In contrast to the skull of modern snakes ( Macrostomata ), the upper jaw (premaxillary and maxillary) of Wonambi was still relatively firmly connected to the rest of the skull. Also had Wonambi still a Jugale ( "cheekbone"), a typically upper rear end of the maxilla ansitz forming bone of the skull, which is completely reduced in modern snakes. Furthermore, the wing bone (pterygoid) shows a relatively short joint pit for the basipterygoid joint, while modern snakes have elongated hollows in which the pterygoid can slide back and forth on the anterior cerebral skull during the swallowing process. All of these are indications that the skull of Wonambi must have been significantly less mobile than that of modern snakes.

Way of life

Like all non colubroids snakes had Wonambi no fangs . Because of this and because of their size, it is assumed, in analogy to the recent boas and pythons , that Madtsoiiden and thus also wonambi were terrestrial strangler snakes that occasionally killed and ate larger mammals. However, so far there have been no further concrete indications for the admissibility of such an analogy. Alternatively, a way of life is proposed for Wonambi that is similar to that of the recent Australian arafura warthog ( Acrochordus arafurae ). Although it kills its prey by choking, it is an aquatic snake that feeds almost exclusively on relatively small fish. This hypothesis would be supported by the fact that Wonambi had a relatively small skull in relation to body size with weakly built jaws that would not have got along well with large prey. The less pronounced cranial kinetics also speaks against larger prey, as the jaws could not have been opened far as much as in modern snakes. Wonambi may have hunted fish in lagoon-like coastal waters. In the caves in which the remains of W. naracoortensis were found, there could have been permanent water at that time, making them an attractive shelter. The increasing drought in southern Australia towards the end of the Pleistocene could eventually have led to the extinction of the great snakes.

Systematics and fossil record

External system

Wonambi is usually assigned a very basal position within the snakes. It is probably related to a number of other "primitive" and extinct species of snakes from South America , Africa and India and is classified with them in the family Madtsoiidae . This means that despite its external similarity to today 's pythons and boas , it is not closely related to them (see →  Convergence ). The origin of the Madtsoiiden lies on the old large southern continent of Gondwana . Most of the finds come from the Upper Cretaceous and from the turn of the Eocene to the Oligocene the group is no longer proven outside Australia. Wonambi was therefore a living fossil , a relic occurrence of the Madtsoiiden, which was able to persist in the increasingly geographically isolated Australia until the recent Cenozoic. However, an alternative hypothesis sees Wonambi as a basal modern snake within the macrostomata .

species

Two types are known. Wonambi naracoortensis Smith 1976 is the type species of the genus and both the geologically younger and the more common. It is known from several localities in South Australia and New South Wales , which are mostly karst caves with Pleistocene deposits ("cave earth"), including the type locality , the caves of Naracoorte , which give the species its name. The oldest occurrence of Wonambi naracoortensis dates to the late Miocene or early Pliocene , the youngest to the late Pleistocene or even early Holocene . Wonambi should have been a contemporary of the first humans in Australia.

The second species, Wonambi barriei Scanlon in Scanlon & Lee 2000, is so far only known from the Lower Miocene of Riversleigh in the state of Queensland . It is named after the Australian private collector and autodidact John Barrie, who dug up, prepared and partly scientifically processed important finds of the genus.

Wonambi naracoortensis differs from its sister species W. barriei mainly in its size, with trunk vertebrae often more than 3 centimeters wide and an estimated total body length of more than 5 meters. The trunk vertebrae of adult specimens of W. barriei , however, are less than 1.5 centimeters wide and their total body length was less than 3 meters. In W. naracoortensis the vertebral hole (the point of passage of the spinal cord ) is small in relation to the vertebra, in W. barriei it is large. Furthermore, W. barriei has a relatively large, noticeable foramen in the caudal surface of the neural arch lateral to the zygantrum ( parazygantral foramen ). In W. naracoortensis there are often several, but relatively inconspicuous foramina that can hardly be distinguished from the dimple-like depressions in the said region of the neural arch. The zygapophyses of W. naracoortensis are about 25 ° more upright than in W. barriei , where the inclination is only 20 °, and while the palatine (a palatal bone) of W. naracoortensis is relatively wide, it is with W. barriei rather narrow.

Remarks

I. The paradiapophysis is a lateral process of the squamate vertebra, formed from the diapophysis (dorsal) and parapophysis (ventral), which articulates with the proximal end of the rib.

Individual evidence

  1. ^ A b Meredith J. Smith: Small fossil vertebrates from Victoria Cave, Naracoorte, South Australia. IV. Reptiles. Transactions of the Royal Society of South Australia. Vol. 100, No. 1, 1976, pp. 39-51 ( BHL ).
  2. ↑ Emanuel Tschopp: Nomenclature of Vertebral Laminae in Lizards, with Comments on Ontogenetic and Serial Variation in Lacertini (Squamata, Lacertidae). In: PLoS ONE. Vol. 11, No. 2, 2016, e79420, doi: 10.1371 / journal.pone.0149445
  3. ^ A b John D. Scanlon: Cranial morphology of the Plio-Pleistocene giant madtsoiid snake Wonambi naracoortensis. Acta Palaeontologica Polonica. Vol. 50, No. 1, 2005, pp. 139-180 ( online ).
  4. ^ A b D. John Barrie: Skull elements and additional remains of the Pleistocene boid snake Wonambi naracoortensis. Memoirs of the Queensland Museum. Vol. 28, No. 1, 1990, pp. 139-151 ( BHL ).
  5. ↑ a b c d e f g John D. Scanlon, Michael SY Lee: The Pleistocene serpent Wonambi and the early evolution of snakes. Nature. Vol. 403, 2000, pp. 416-420, doi: 10.1038 / 35000188 (alternative full text access : ResearchGate ).
  6. ^ A b John D. Scanlon: Skull of the large non-macrostomatan snake Yurlunggur from the Australian Oligo-Miocene. Nature. Vol. 439, 2006, pp. 840-842, doi: 10.1038 / nature04137 (alternative full text access: ResearchGate ).
  7. ^ Menna Jones, Chris R. Dickman, Michael Archer, Predators with Pouches: The Biology of Carnivorous Marsupials. CSIRO Publishing, Collingwood 2003, ISBN 0-643-06634-9 , p. 119
  8. ^ Allison Y. Hsiang, Daniel J. Field, Timothy H. Webster, Adam DB Behlke, Matthew B. Davis, Rachel A. Racicot, Jacques A. Gauthier: The origin of snakes: Revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record. BMC Evolutionary Biology. Vol. 15, 2015, Item No. 87, doi: 10.1186 / s12862-015-0358-5 .
  9. ^ John D. Scanlon: The Basicranial Morphology of Madtsoiid Snakes (Squamata, Ophidia) and the Earliest Alethinophidia (Serpentes). Journal of Vertebrate Paleontology. Vol. 23, No. 4, 2003, pp. 971-976, doi: 10.1671 / 24 (alternatively: JSTOR 4524401 ).
  10. ↑ cf. also Madtsoiidae in the Paleobiology Database, accessed April 19, 2016
  11. ↑ Olivier Rieppel, Arnold G. Kluge, Hussam Zaher: Testing the Phylogenetic Relationships of the Pleistocene Snake Wonambi naracoortensis Smith. Journal of Vertebrate Paleontology. Vol. 22, No. 4, 2002, pp. 812-829, doi : 10.1671 / 0272-4634 (2002) 022 [0812: TTPROT] 2.0.CO; 2 (alternatively: JSTOR 4524280 ).
  12. ^ Wonambi naracoortensis in the Paleobiology Database, accessed April 19, 2016
  13. ↑ Wonambi barriei in the Paleobiology Database, accessed April 19, 2016