Wakaleo schouteni: A new species of Marsupial Lion from the Oligo-Miocene Riversleigh World Heritage Area of Queensland, Australia.

Marsupial Lions, Thylacoleonidae, are an extinct group of carnivorous Mammals from the Cainozoic of Australia. Many of these animals were large in size and showed dentition associated with a hypercarnivorous diet (diet composed almost entirely of meat), and are assumed to have been the top predators in the ecosystems where they lived. Members of the genus Wakaleo are dog-sized animals known from the Oligocene and Miocene of South Australia, Northern Territory and Queensland.

In a paper published in the Journal of Systematic Biology on 6 December 2017, Anna Gillespie, Michael Archer and Suzanne Hand of the PANGEA Research Centre at the University of New South Wales, describe a new species of Wakaleo from the late Oligocene to early Miocene sediments of the Riversleigh World Heritage Area in Queensland, Australia. 

The new species is named Wakaleo schouteni, in honour of palaeoartist Peter Schouten, for his reconstructions of the Riversleigh fauna and other prehistoric Australian animals. It is described from an almost complete skull, preserved in two halves, with most molar teeth intact, plus several fragmentary jaw sections, and a left and right humerus (from separate locations).

Wakaleo schouteni; (A) left lateral view; (B) left lateral view with jugal removed (hatched area) and M4 included; (C), posterior view. Abbreviations: al, alisphenoid; C, canine; eam, external auditory meatus; fm, foramen magnum; for, foramen rotundum; fr, frontal; iof, infraorbital foramen; jg, jugal; lac, lacrimal; lacf, lacrimal foramen; M, molar; max, maxilla; mf, maxillary foramen; mp, mastoid process; ms, mastoid; nc, nuchal crest; ns, nasal; oc, occipital condyle; os, orbitosphenoid; P, premolar; pal, palatine; par, parietal; pgp, postglenoid process; pmx, premaxilla; pop, paroccipital process; pt, pterygoid; ptp, pterygoid process of the alisphenoid; sc, sagittal crest; so, supraoccipital; sof, sphenorbital fissure; sop, supraorbital process; spf, sphenopalatine foramen; sq,squamosal; ssf, subsquamosal fossa; tvc, transverse canal. Gillespie et al. (2017). 

Wakaleo schouteni is one of the smallest members of the genus, with a total skull length of 164 mm, and an estimated living mass of between 22.6 and 24.0 kg (comparable to a Dalmation or Collie Dog). It is also one pf the earliest known members of the group, and has somewhat generalised dentition, something generally associated with an omnivorous diet, rather than a carnivorous one. This suggests that the genus may have began as small omnivorous animals with only a low amount of meat in their diet, then grown larger over time as they became more-and-more specialised for carnivorey, a pattern known from a variety of other groups.

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Gumardee richi & Gumardee springae: Two new species of Potoroos from the Oligo-Miocene of Queensland.

Potoroos, Potoroidae, are Rabbit-sized members of the Macropodiformes, the group which also includes Kangaroos and Wallabies. They are essentially similar to Kangaroos in appearance, but smaller and have simpler dentition, leading to suggestions that they might be ancestral to the larger Macropodiformes. The groups includes four species of Recent Potaroos, one of which become extinct in the nineteenth century, six species of recent Bettongs, two of which are now extinct, two species of Rat Kangaroo, one of which became extinct in the twentieth century, as well as a number of fossil forms, dating back as far as the Oligocene.

In a paper published in the Memoirs of Museum Victoria on 22 July 2016, Kenny Travouillon of the Western Australian Museum and the School of Earth Sciences at the University of Queensland, Kaylene Butler, also of the School of Earth Sciences at the University of Queensland, and Michael Archer and Suzanne Hand of the PANGEA Research Centre at the University of New South Wales, describe two new species of Potoroo from the late Oligocene to early Miocene deposits of the Riversleigh World Heritage Area in northwestern Queensland, Australia. Both species are placed in the genus Gumardee, which previously contained one species, Gumardee pascuali, also from the Riversleigh World Heritage deposits, and some loose teeth assigned only to genus level from the Namba Formation of Lake Pinpa, South Australia.

The first new species is named Gumardee richi, in honour of Thomas Rich of Museum Victoria, for his long and significant contribution to Australian palaeontology. The species is described from a partial left juvenile maxilla, a left juvenile dentary, a partial juvenile right dentary, a left maxilla and two further left dentaries. These were located at two sites, Dirk’s Towers and Quantum Leap, both of which are interpreted as being Early Miocene in age.

Gumardee richi, first specimen, partial left juvenile maxilla with P3 in crypt, dP2-3 and M1-2: (A) buccal, (B) lingual, and (C) occlusal (stereopair) views; second specimen, left maxilla with M1-4: (D) buccal, (E) lingual, and (F) occlusal (stereopair) views. Scale bar equals 10 mm. Travouillon et al. (2016).

The second new species is named Gumardee springae, in honour of Kirsten Spring of the Geosciences Program at the Queensland Museum, in recognition of her skilled and careful management of the large and diverse Riversleigh fossil collections. This species is described from two partial juvenile skulls, one with an associated left maxilla, as well as a large number of jaw fragments. All of these came from the White Hunter Site, which is interpretted as being Late Oligocene in age.

Gumardee springae, first specimen, partial juvenile skull with left loose P2, dP3, left and right P3 in crypt, M1-3 and associated left maxilla with dP3, P3 in crypt, M1-3: (A) dorsal, and (B) ventral views. Scale bar equals 10 mm. Travouillon et al. (2016).

See also...

Reconstructing the diet of a Miocene Thylacinid.                                          Thylacinids (Thylacinidae) were large carnivorous Australian Marsupials that appeared in the...

A 'South American' Marsupial from the early Eocene of Australia.                                Modern Australian Marsupials are generally held to be a distinct evolutionary lineage, distinct from...

What killed the Australian Thylacine.              The Thylacine, also known as the Tasmanian Tiger or Marsupial Wolf, was a large, predatory...

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Dwarf Crocodile remains from the Oligo–Miocene of northwestern Queensland.

The Mekosuchine Crocodile Mekosuchuswhitehunterensis was described from Late Oligocene deposits exposed at the White Hunter Site in the Riversleigh World Heritage Area innorthwestern Queensland. It is interpreted to have been largely terrestrial, and to have been a dwarf species reaching maturity at little over a meter in length. However dwarfism is hard to diagnose in fossil Crocodilian species, as the animals grow throughout their entire lives, only slowing their growth rate when they reach maturity, and because small Crocodillian species tend to be essentially similar to juveniles of larger species.

In a forthcoming paper in the journal Acta Palaeontologica Polonica, available online from 16 January 2015, Michael Stein, Michael Archer and Suzanne Hand of the School of Biological, Earth and Environmental Sciences at the University of New South Wales describe additional material assigned to Mekosuchus whitehunterensis from the Early Miocene Price is Right Site and Late Oligocene Hiatus and LSO sites, also in the Riversleigh World Heritage Area.

The original material from the White Hunter Site comprised entirely cranial material. The new material from the Price is Right Site comprises a left maxilla and dentary (upper and lower jaw bones) which appear to belong to the same species, as well as a series of five associated cervical vertebrae. The material from the Hiatus Site comprises two vertebrae which appear to be from the same species as those at the Price is Right Site, while the LSO site material comprises a single vertebra, again apparently of the same species.

Rostra of Mekosuchine Crocodile Mekosuchus whitehunterensis.(A) Left maxilla in buccal (A₁) and ventral (A₂) views. (B) Left dentary in lingual (B₁), dorsal (B₂), and buccal (B₃) views. Scale bars 5 cm. Stein et al. (2015).

Vertebrae are much more useful in assessing the maturity of a Crocodilian than cranial material, as the neurocentral suture closes (mineralizes) in mature individuals. The new vertebrae appear to come from a mature individual, and have a mean anterioposterior length (front-to-back length, thickness) of 19.3 mm. The most complete known skull of Mekosuchus whitehunterensis is about 10 cm in length, which combined with the proportions of the vertebrae suggest a mature individual measuring about 60 cm, considerably smaller than the smallest modern Crocodilians, Osteolaminus and Paleosuchus, both of which typically exceed a meter in length at maturity.

Vertebrae of Mekosuchine Crocodile Mekosuchus whitehunterensisin left (A₁–H₁) and right (A₂–H₂) views. (A) Axis vertebra. (B) Third cervical vertebra. (C) Fourth cervical vertebra. (D) Sixth cervical vertebra. (E) Ninth cervical vertebra. (F) Third thoracic vertebra. (G) Third cervical vertebra. (H) Eighth cervical vertebra. Arrows indicate extent of the neurocentral suture. Scale bars 2 cm. Stein et al. (2015).

The cervical vertebrae show significantly enlarged muscle attachments, suggesting that the living animal had powerful neck muscles. This has implications for the feeding strategy of the living animal. Modern Crocodiles remove meat from prey animals in two ways. Firstly they body role, taking a firm grip of their prey they rotate their entire bodies in order to tear digestible pieces from the prey. However this strategy is seldom employed by small Crocodilians, which lack the mass use this strategy effectively. It is also a feeding method best suited to an aquatic environment, where the water cushions the body from any damage, and could be rather more risky in a terrestrial environment (where Mekosuchus whitehunterensisis thought to have fed) as friction with the ground could potentially lead to damage to the body or limbs. Secondly Crocodiles can remove meat from a prey animal by vigorously shaking their heads in a manner similar to a Dog. This is a strategy of limited usefulness in an aquatic environment, where the prey is likely to simply move with the head, but can be very effective on dry land, where the prey is held down to some extent by gravity and experiences friction with the ground. The enlarged neck muscles of Mekosuchus whitehunterensis would seem suitable for such a feeding method, supporting the idea that it hunted or scavenged away from the water.

See also…

A Baurusuchid Crocodyliforme with preserved stomach contents from the Late Cretaceous of Brazil.                                                                     The Adamantina Formation from the Late Cretaceous of southern Brazil produces a wide variety of Crocodyliformes, including semi-aquatic...

A Tethysuchian Crocodyliform from the Early Cretaceous of the Isle of Wight.

The Tethysuchians were a group of largely marine Crocodyliforms that are reasonably well known from the Middle and Late Cretaceous, with one group, the Dyrosauridae surviving the End Cretaceous extinction...

The Rosso Ammonitico Veronese Crocodylomorph.

The Rosso Ammonitico Veronese is a red nodular limestone found on the Trento Plateau in northern Italy, and Middle to Late Jurassic in age. It is noted for its numerous Ammonite fossils, but also produces occasional Marine Reptiles, notably Thalattosuchian Crocodylomorphs and Plesiosaurians. The earliest recorded discovery of such a Reptile is a Crocodylian...

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A giant Platypus from the Miocene of northwestern Queensland.

Platypus (Ornithorhynchidae) are semi-aquatic Monotremes from eastern Australia and Tasmania. Like other Monotremes they are egg-layers, and lack several other adaptations seen in Marsupial and Placental Mammals. Monotremes are thought to have branched from the Mammal family tree around 220 million years ago, and are sometimes referred to as 'living fossils', though this is somewhat inaccurate, as nothing resembling a modern Platypus or Echidna is thought to have existed that long ago; rather the group have followed their own, separate, evolutionary path for a long time. The single species of modern Platypus, Ornithorhynchus anatinus, resembles a small Otter, but with a large, flat tail similar to that of a Beaver, and a leathery beak resembling that of a Duck. This beak is an electroreceptive organ, used to detect buried invertebrates, upon which the Platypus feeds. The male Platypus has venomous spurs on its hind legs.

In a paper published in the Journal of Vertebrate Paleontology on 5 November 2013, Rebecca Pian, Michael Archer and Suzanne Hand of the School of Biological, Earth and Environmental Sciences  at the University of New South Wales, describe a new species of fossil Platypus from the Two Trees Site in the Riversleigh World Heritage Area in northwestern Queensland, Australia.

The new species is placed in the genus Obdurodon, and given the specific name tharalkooschild; the Platypus being the child of the Water Rat Biggon and the Duck Tharalkoo in local Aboriginal mythology. Obdurodon tharalkooschild is described from a single molar. This is somewhat counterintuitive, as modern Platypus are toothless, however this is the third species described in the genus Obdurodon, and the teeth are considered to be quite distinctive.

(A–E) Obdurodon tharalkooschild., first lower molar. (A and B) Stereopair, occlusal view; (C) anterior view; (D) buccal view; (E) lingual view. (F) Obdurodon insignis, first lower molar, occlusal view. Pian et al. (2013).

The dating of the Two Trees Site is somewhat controversial. It is generally thought to be middle Miocene in age, but some authors have argued that it is late Miocene or even Pliocene in age.

See also A 'South American' Marsupial from the early Eocene of Australia, What killed the Australian Thylacine and Walking with Giant Wombats.

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