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

Rougier, Guillermo W.; Martinelli, Agustín G.; Forasiepi, Analía M.; Novacek, Michael J.

doi:10.1206/0003-0082(2007)507[1:njmfpa]2.0.co;2

Cited by 100 publications

(48 citation statements)

References 12 publications

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“…Furthermore, all of the aforementioned trees united the Chinese ''primitive triconodont'' Hadrocodium with monotremes, contrary to the majority opinion (5,6,24,27,48) that monotreme affinities lie with the Gondwanan clade, Australosphenida. The original incarnation of the present morphological data sets (27) Backbone constraints were used to define these alternatives for morphol439 and morphol441, both with the remainder of the tree topology unconstrained or with monotremes constrained to group within Australosphenida (ЉAustra-losphenida-constrainedЉ).…”

Section: Resultsmentioning

confidence: 89%

Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas

Phillips

Bennett

Lee

2009

Proc. Natl. Acad. Sci. U.S.A.

125

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The semiaquatic platypus and terrestrial echidnas (spiny anteaters) are the only living egg-laying mammals (monotremes). The fossil record has provided few clues as to their origins and the evolution of their ecological specializations; however, recent reassignment of the Early Cretaceous Teinolophos and Steropodon to the platypus lineage implies that platypuses and echidnas diverged >112.5 million years ago, reinforcing the notion of monotremes as living fossils. This placement is based primarily on characters related to a single feature, the enlarged mandibular canal, which supplies blood vessels and dense electrosensory receptors to the platypus bill. Our reevaluation of the morphological data instead groups platypus and echidnas to the exclusion of Teinolophos and Steropodon and suggests that an enlarged mandibular canal is ancestral for monotremes (partly reversed in echidnas, in association with general mandibular reduction). A multigene evaluation of the echidna-platypus divergence using both a relaxed molecular clock and direct fossil calibrations reveals a recent split of 19 -48 million years ago. Platypus-like monotremes (Monotrematum) predate this divergence, indicating that echidnas had aquatically foraging ancestors that reinvaded terrestrial ecosystems. This ecological shift and the associated radiation of echidnas represent a recent expansion of niche space despite potential competition from marsupials. Monotremes might have survived the invasion of marsupials into Australasia by exploiting ecological niches in which marsupials are restricted by their reproductive mode. Morphology, ecology, and molecular biology together indicate that Teinolophos and Steropodon are basal monotremes rather than platypus relatives, and that living monotremes are a relatively recent radiation.calibration ͉ molecular dating ͉ Monotremata ͉ niche ͉ phylogeny

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Section: Resultsmentioning

confidence: 89%

Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas

Phillips

Bennett

Lee

2009

Proc. Natl. Acad. Sci. U.S.A.

125

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“…This angle is also absent on the dentary of Bishops and Henosferus [40,42]. The possible exception is Eomaia, whose dentary seems to have an angle in the same condition as that of Sasayamamylos [4].…”

Section: Comparison and Discussionmentioning

confidence: 90%

A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan

et al. 2013

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We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the 'Lower Formation' of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3 -4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian.

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“…Revisions to the matrix were made on the basis of corrections and criticisms by Woodburne et al (2003), Rougier et al (2007), Rowe et al (2008) and Phillips et al (2009). The final matrix included 104 taxa and 438 characters.…”

Section: Methodsmentioning

confidence: 99%

“…These include: from the Aptian Flat Rocks locality in Victoria, the ausktribosphenids Ausktribosphenos nyktos (Rich et al, 1997) and Bishops whitmorei (Rich et al, 2001a), the monotreme Teinolophos trusleri (Rich et al, 1999(Rich et al, , 2001b, and the multituberculate Corriebaatar marywaltersae (Rich et al, 2009); from the Albian Dinosaur Cove locality in Victoria, the partial humerus of (the possible monotreme) Kryoryctes cadburyi (Pridmore et al, 2005); and from Lightning Ridge in New South Wales a very large, mammal-like isolated tooth (Clemens et al, 2003). Most recent phylogenetic analyses have placed ausktribosphenids and monotremes within a larger Gondwanan radiation termed Australosphenida (Luo et al, 2001(Luo et al, , 2002(Luo et al, , 2007aMartin and Rauhut, 2005;Rougier et al, 2011;Wood and Rougier, 2005), together with the early Jurassic (Toarcian) (Cúneo et al, 2013) South American Asfaltomylos (Rauhut et al, 2002) and Henosferus (Rougier et al, 2007), and the middle Jurassic (Bathonian) Ambondro mahabo (Flynn et al, 1999) from Madagascar. Some authors, however, have questioned the inclusion of monotremes within Australosphenida (Pascual et al, 2002;Rich et al, 2002;Rowe et al, 2008;Woodburne, 2003).…”

Section: Introductionmentioning

confidence: 99%

The upper dentition and relationships of the enigmatic Australian Cretaceous mammal Kollikodon ritchiei

Pian¹,

Archer²,

Hand³

et al. 2016

MMV

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Mesozoic mammals from Australia are rare, so far only known from the Early Cretaceous, and most are poorly represented in terms of dentitions much less cranial material. No upper molars of any have been described. Kollikodon ritchiei is perhaps the most bizarre of these, originally described on the basis of a dentary fragment with three molars. Here we describe a second specimen of this extremely rare taxon, one that retains extraordinarily specialised upper cheekteeth (last premolar and all four molars). Each molar supports rows of bladeless, rounded cuspules many of which exhibit apical pits that may be the result of masticating hard items such as shells or chitin. Reanalysis of the phylogenetic position of this taxon suggests, based on a limited number of apparent synapomorphies, that it is an australosphenidan mammal and probably the sister group to Monotremata. This reanalysis also supports the view that within Monotremata, tachyglossids and ornithorhynchids diverged in the early to middle Cenozoic.

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

Cited by 100 publications

References 12 publications

Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas

Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas

A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan

The upper dentition and relationships of the enigmatic Australian Cretaceous mammal Kollikodon ritchiei

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