Were There Miocene Meridiolestidans? Assessing the Phylogenetic Placement of Necrolestes patagonensis and the Presence of a 40 Million Year Meridiolestidan Ghost Lineage

O’Meara, Rachel N.; Thompson, Richard S.

doi:10.1007/s10914-013-9252-3

Cited by 21 publications

(16 citation statements)

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“…Because monotremes are an early‐divergent clade of extant mammals (Luo et al, ; Phillips et al, ; O'Meara and Thompson, ), the newly documented structural relationship of the osseous and membranous inner ear labyrinths of Ornithorhynchus and Tachyglossus are important for comparative inference of inner ear structures of extinct Mesozoic mammaliaforms. Furthermore, the osteological characters should be incorporated into phylogenetic character matrices for inferring mammaliaform relationships (e.g., Luo et al, ; Ekdale and Rowe, ; Macrini et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Phylogenetically, basal mammaliaforms like Sinoconodon , Morganucodon and Haldanodon are positioned between extant monotremes and extant non‐mammalian amniotes (O'Meara and Thompson, ). Accordingly, parsimony suggests that basal mammaliaforms possessed characteristics shared by both diapsids and monotremes.…”

Section: Discussionmentioning

confidence: 99%

“…Monotremes (i.e., the platypus and the short and long beaked echidnas) are an early-divergent clade of crown Mammalia that are different from extant therians (i.e., marsupials and placentals) in many anatomical structures and functions, such as interclavicular bones, epipubic bones, cloaca and laying shelled eggs (Archer et al, 1985;Rowe, 1988;Zeller, 1999;Luo et al, 2001;Musser, 2003;Mikoleit, 2004;Augee et al, 2006;Grant, 2007;Rowe et al 2008, Phillips et al, 2009Ashwell, 2013;O'Meara and Thompson, 2014). In addition, several inner ear features distinguish monotremes from therians (Pritchard, 1881;Denker, 1901;Gray, 1908;Zeller, 1989;Jørgensen and Locket, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

Schultz

Zeller

Luo

2016

Journal of Morphology

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The monophyletic clade Monotremata branches early from the rest of the mammalian crown group in the Jurassic and members of this clade retain many ancestral mammalian traits. Thus, accurate and detailed anatomical descriptions of this group can offer unique insight into the early evolutionary history of Mammalia. In this study, we examine the inner ear anatomy of two extant monotremes, Ornithorhynchus anatinus and Tachyglossus aculeatus, with the primary goals of elucidating the ancestral mammalian ear morphology and resolving inconsistencies found within previous descriptive literature. We use histological serial sections and high-resolution microcomputed tomography (µCT) for correlating soft tissue features of the vestibule and cochlea to the osseous labyrinth endocast. We found that in both monotremes the scala tympani coils to a lesser degree than scala vestibuli and scala media, although all three scalae show an apical coil inside the osseous cochlear tube. The helicotrema (conduit between scala tympani and scala vestibuli) is in subapical position, and the cochlear and lagenar ganglia and their associated nerve fibers are not enclosed by bone. In comparison, in extant therian mammals (i.e., marsupials and placentals) the helicotrema is located at the apex of the osseous cochlear canal, the three scalae coil to the same degree and the cochlear ganglion is enclosed by the primary bony lamina. Whether the lagenar ganglion is lost in therian mammals or integrated into the cochlear ganglion is still debated. The presence of a sensory lagenar macula at the apex of the membranous cochlear duct, innervated by a separate lagenar nerve and ganglion is a plesiomorphic condition of amniotes that monotremes share. A separate osseous lagenar canaliculus for the lagenar nerve, and the coiling of the distended lagenar sac at the end of the cochlear duct are autapomorphies of monotremes. Based on our findings we hypothesize that the ancestral inner ear of stem mammaliaforms is characterized by a straight or slightly curved osseous cochlear canal, a lagenar macula, lagenar nerve fibers separated from a larger bundle of cochlear nerve fibers, the presence of an organ of Corti and an intra-otic cochlear ganglion suspended by membranous connective tissue. Among the major Mesozoic clades of crown mammals, cladotherians and gondwanatherians most likely acquired a fully functioning organ of Corti but lost the sensory lagenar macula, like extant therians. However, Mesozoic spalacotherioids, multituberculates and eutriconodonts likely retained the mammaliaform condition. J. Morphol. 278:236-263, 2017. © 2016 Wiley Periodicals,Inc.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

Schultz

Zeller

Luo

2016

Journal of Morphology

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“…1.14 and 4.1); all other specimens have lost their cusps through wear, and hence uncertainties remain regarding cusp homologies (Sánchez-Villagra and Kay 1997 ; Zimicz 2011 ; Goin and Abello 2013 ). A priori interpretations regarding cusp homologies that lack clear evidential support may bias phylogenetic analyses towards particular topologies (O’Meara and Thompson 2014 ). Assumptions that, for example, the labialmost cuspid of the trigonid in argyrolagids is a neomorphic “ectostylid” (as in Zimicz 2011 ; Goin and Abello 2013 ) rather than the protoconid (as in Sánchez-Villagra and Kay 1997 ), remain questionable in the absence of unworn argyrolagid dentitions that would clarify the topological and occlusal relations between cusps.…”

Section: Affinities Of Argyrolagoidsmentioning

confidence: 99%

The Skull of Epidolops ameghinoi from the Early Eocene Itaboraí Fauna, Southeastern Brazil, and the Affinities of the Extinct Marsupialiform Order Polydolopimorphia

Beck

2016

J Mammal Evol

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The skull of the polydolopimorphian marsupialiform Epidolops ameghinoi is described in detail for the first time, based on a single well-preserved cranium and associated left and right dentaries plus additional craniodental fragments, all from the early Eocene (53–50 million year old) Itaboraí fauna in southeastern Brazil. Notable craniodental features of E. ameghinoi include absence of a masseteric process, very small maxillopalatine fenestrae, a prominent pterygoid fossa enclosed laterally by a prominent ectopterygoid crest, an absent or tiny transverse canal foramen, a simple, planar glenoid fossa, and a postglenoid foramen that is immediately posterior to the postglenoid process. Most strikingly, the floor of the hypotympanic sinus was apparently unossified, a feature found in several stem marsupials but absent in all known crown marsupials. “Type II” marsupialiform petrosals previously described from Itaboraí plausibly belong to E. ameghinoi; in published phylogenetic analyses, these petrosals fell outside (crown-clade) Marsupialia. “IMG VII” tarsals previously referred to E. ameghinoi do not share obvious synapomorphies with any crown marsupial clade, nor do they resemble those of the only other putative polydolopimorphians represented by tarsal remains, namely the argyrolagids. Most studies have placed Polydolopimorphia within Marsupialia, related to either Paucituberculata, or to Microbiotheria and Diprotodontia. However, diprotodonty almost certainly evolved independently in polydolopimorphians, paucituberculatans and diprotodontians, and Epidolops does not share obvious synapomorphies with any marsupial order. Epidolops is dentally specialized, but several morphological features appear to be more plesiomorphic than any crown marsupial. It seems likely Epidolops that falls outside Marsupialia, as do morphologically similar forms such as Bonapartherium and polydolopids. Argyrolagids differ markedly in their known morphology from Epidolops but share some potential apomorphies with paucituberculatans. It is proposed that Polydolopimorphia as currently recognised is polyphyletic, and that argyrolagids (and possibly other taxa currently included in Argyrolagoidea, such as groeberiids and patagoniids) are members of Paucituberculata. This hypothesis is supported by Bayesian non-clock phylogenetic analyses of a total evidence matrix comprising DNA sequence data from five nuclear protein-coding genes, indels, retroposon insertions, and morphological characters: Epidolops falls outside Marsupialia, whereas argyrolagids form a clade with the paucituberculatans Caenolestes and Palaeothentes, regardless of whether the Type II petrosals and IMG VII tarsals are used to score characters for Epidolops or not. There is no clear evidence for the presence of crown marsupials at Itaboraí, and it is possible that the origin and early evolution of Marsupialia was restricted to the “Austral Kingdom” (southern South America, Antarctica, and Australia).Electronic supplementary materialThe online version of this article (doi:10.1...

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“…Each shows many features associated with fossoriality, such as forelimbs with extreme myological and osteological specialization (Yalden, ; Whidden, ) and degenerate vision. Independently evolved cases of fossoriality are known throughout mammalian evolutionary history, from the Jurassic ( Fruitafossor , Luo and Wible, ; Haldanodon , Ruf et al, ; Docofossor , Luo et al, ) to the Cenozoic ( Necrolestes , O'Meara and Thompson, ; Epoicotherium , Rose and Emry, ).…”

Section: Introductionmentioning

confidence: 99%

Convergence vs. Specialization in the ear region of moles (mammalia)

Crumpton

Kardjilov

Asher

2015

Journal of Morphology

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We investigated if and how the inner ear region undergoes similar adaptations in small, fossorial, insectivoran-grade mammals, and found a variety of inner ear phenotypes. In our sample, afrotherian moles (Chrysochloridae) and the marsupial Notoryctes differ from most other burrowing mammals in their relatively short radii of semicircular canal curvature; chrysochlorids and fossorial talpids share a relatively long interampullar width. Chrysochlorids are unique in showing a highly coiled cochlea with nearly four turns. Extensive cochlear coiling may reflect their greater ecological dependence on low frequency auditory cues compared to talpids, tenrecids, and the marsupial Notoryctes. Correspondingly, the lack of such extensive coiling in the inner ear of other fossorial species may indicate a greater reliance on other senses to enable their fossorial lifestyle, such as tactile sensation from vibrissae and Eimer's organs. The reliance of chrysochlorids on sound is evident in the high degree of coiling and in the diversity of its mallear types, and may help explain the lack of any semiaquatic members of that group. The simplest mallear types among chrysochlorids are not present in the basal-most members of that clade, but all extant chrysochlorids investigated to date exhibit extensive cochlear coiling. The chrysochlorid ear region thus exhibits mosaic evolution; our data suggest that extensive coiling evolved in chrysochlorids prior to and independently of diversification in middle ear ossicle size and shape.

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Were There Miocene Meridiolestidans? Assessing the Phylogenetic Placement of Necrolestes patagonensis and the Presence of a 40 Million Year Meridiolestidan Ghost Lineage

Cited by 21 publications

References 54 publications

Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

The Skull of Epidolops ameghinoi from the Early Eocene Itaboraí Fauna, Southeastern Brazil, and the Affinities of the Extinct Marsupialiform Order Polydolopimorphia

Convergence vs. Specialization in the ear region of moles (mammalia)

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