New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships

By G. Rougier, A. Martinelli, A. Forasiepi, M. Novacek. 2007

117 citations recorded by the source corpus.

Abstract A new mammal, Henosferus molus, n.gen. and n.sp., from the Callovian–Oxfordian (latest Middle to earliest Late Jurassic) Cañadón Asfalto Formation from Chubut Province (Argentina) is described. This taxon corresponds to a new species clearly different from Asfaltomylos patagonicus from the same locality and stratigraphic level. This new species is based on three lower jaws with relatively well-preserved dentition. The lower jaw shows a primitive morphology having a Meckelian groove, a prominent medial flange associated with a lateral ridge of the dentary, and a deep dentary trough, which possibly indicates the presence, even though reduced, of postdentary bones still attached to the dentary. The lower dental formula is i4, c1, p5, m3. The premolars are simple, bearing a main cusp, while the molars appear to be tribosphenic, with an obtuse to right-angled trigonid and a basined talonid with three cusps. This association of plesiomorphic features in the jaw and derived features in the molars is documented in several taxa of the recently proposed Australosphenida. A phylogenetic analysis of mammaliaforms nests the new species with Asfaltomylos from the same locality and stratigraphic level; Henosferidae, new family, is recognized for Asfaltomylos and Henosferus, representing the basal radiation of Australosphenida. Henosferidae is the sister group to Ambondro from the Middle Jurassic of Madagascar, which, in agreement with previous phylogenies, is the sister taxon to the remaining australosphenidans. Additionally, our phylogenetic analysis does not support the inclusion of australosphenidans within eutherians. Henosferids likely retained some connection of the postdentary elements with the dentary; therefore, if the inclusion of Monotremata within Australosphenida is confirmed, final freeing of the postdentary elements and development of a tri-ossicular middle ear would be convergent events in Monotremata and Theria. Finally, the distinctiveness of the yet sparse South American record of Jurassic mammals when compared with the slightly better documented Cretaceous data is emphasized. The clear faunistic break between the Middle Jurassic and Early/Late Cretaceous underlies our rudimentary understanding of the evolution of Mesozoic mammals in Gondwana.

Subfields: Ecology, Evolution, Behavior and Systematics, Paleontology

View Paper: https://www.semanticscholar.org/paper/f73e9b207b79f574450f8502d5333770c194ac66

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Ecology, Evolution, Behavior and Systematics

In Paleontology

Citations in the corpus

The Eutherian Mammal Maelestes gobiensis from the Late Cretaceous of Mongolia and the phylogeny of cretaceous eutheria (2009, background): “Wible et al. did not include any of the Jurassic and Cretaceous Gondwanan mammals (Am- 54 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 327 bondro Flynn et al., 1999, Ausktribosphenos Rich et al., 1997, Bishops Rich et al., 2001, Asfaltomylos Rauhut et al., 2002, Henosferus Rougier et al., 2007a) ”
Mammals from the Allen Formation, Late Cretaceous, Argentina (2009, background): “The australosphenidans have only distant afﬁnities with regard to any of the mammals that are dominant in the Late Cretaceous, and the triconodonts are utterly unrelated to all of them (Rougier et al., 2001; Luo et al., 2002; Meng et al., 2003; Kielan-Jaworowska et al., 2004; Rougier et al., 2007c).”