Epipubic bones in eutherian mammals from the Late Cretaceous of Mongolia

Novacek, Michael J.; Rougier, Guillermo W.; Wible, John R.; McKenna, Malcolm C.; Dashzeveg, Demberelyin; Horovitz, Inés

doi:10.1038/39020

Cited by 110 publications

(77 citation statements)

References 16 publications

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“…The primitive lower incisor count for eutherians is possibly four [11,47]. Several early eutherians, such as Bobolestes, Eomaia, Eozhelestes and Juramaia have four lower incisors [3,4,44]; there are also some later forms, such as Asioryctes, Kulbeckia and Ukhaatherium, which have four lower incisors [30,48,49], although one of the earlier eutherian mammals, Acristatherium, has only three incisors [5]. Sasayamamylos kawaii shows a polymorphic intermediate state between primitive forms with four lower incisors and those with three; this indicates that the reduction in the incisor count in the lineage to which Sasayamalestes belongs started from i4.…”

Section: Comparison and Discussionmentioning

confidence: 99%

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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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Section: Comparison and Discussionmentioning

confidence: 99%

“…Infraclass: Eutheria Gill [29] Order: Asioryctitheria Novacek, Rougier, Wible, McKenna, Dashzeveg & Horovitz [30] Family: Incertae sedis Sasayamamylos kawaii gen. et sp. nov. Kusuhashi and Saegusa…”

Section: Systematic Palaeontologymentioning

confidence: 99%

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

et al. 2013

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“…Many paleontologists have considered epipubic bones as evidence that mammaliaforms and early mammals (including early eutherians) carried eggs or young in a pouch or suspended from the abdomen; however, others argue that epipubic bones rather had a function in locomotion as the structure of the pelvis evolved (Novacek et al, 1997;Reilly and White, 2003). Pouches have evolved in both monotremes (e.g.…”

Section: Milk Secretion In the Context Of Synapsid Evolutionmentioning

confidence: 99%

The evolution of milk secretion and its ancient origins

Oftedal

2012

Animal

198

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Lactation represents an important element of the life history strategies of all mammals, whether monotreme, marsupial, or eutherian. Milk originated as a glandular skin secretion in synapsids (the lineage ancestral to mammals), perhaps as early as the Pennsylvanian period, that is, approximately 310 million years ago (mya). Early synapsids laid eggs with parchment-like shells intolerant of desiccation and apparently dependent on glandular skin secretions for moisture. Mammary glands probably evolved from apocrine-like glands that combined multiple modes of secretion and developed in association with hair follicles. Comparative analyses of the evolutionary origin of milk constituents support a scenario in which these secretions evolved into a nutrient-rich milk long before mammals arose. A variety of antimicrobial and secretory constituents were co-opted into novel roles related to nutrition of the young. Secretory calcium-binding phosphoproteins may originally have had a role in calcium delivery to eggs; however, by evolving into large, complex casein micelles, they took on an important role in transport of amino acids, calcium and phosphorus. Several proteins involved in immunity, including an ancestral butyrophilin and xanthine oxidoreductase, were incorporated into a novel membrane-bound lipid droplet (the milk fat globule) that became a primary mode of energy transfer. An ancestral c-lysozyme lost its lytic functions in favor of a role as a-lactalbumin, which modifies a galactosyltransferase to recognize glucose as an acceptor, leading to the synthesis of novel milk sugars, of which free oligosaccharides may have predated free lactose. An ancestral lipocalin and an ancestral whey acidic protein four-disulphide core protein apparently lost their original transport and antimicrobial functions when they became the whey proteins b-lactoglobulin and whey acidic protein, which with a-lactalbumin provide limiting sulfur amino acids to the young. By the late Triassic period (ca 210 mya), mammaliaforms (mammalian ancestors) were endothermic (requiring fluid to replace incubatory water losses of eggs), very small in size (making large eggs impossible), and had rapid growth and limited tooth replacement (indicating delayed onset of feeding and reliance on milk). Thus, milk had already supplanted egg yolk as the primary nutrient source, and by the Jurassic period (ca 170 mya) vitellogenin genes were being lost. All primary milk constituents evolved before the appearance of mammals, and some constituents may have origins that predate the split of the synapsids from sauropsids (the lineage leading to 'reptiles' and birds). Thus, the modern dairy industry is built upon a very old foundation, the cornerstones of which were laid even before dinosaurs ruled the earth in the Jurassic and Cretaceous periods.Keywords: evolution, lactation, milk composition, casein, milk fat globule ImplicationsLactation has an evolutionary origin and biological context within which its secretory processes and milk constituents evolved. This revi...

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“…§ We use Eutheria here as a stem-based taxon including all living or extinct taxa more closely related to extant placental mammals than to extant marsupials. Placentalia is used as a crown group that contains all extant eutherians and their last common ancestor and excludes all other eutherians [e.g., Asioryctitheria (11)]. …”

mentioning

confidence: 99%

Widanelfarasia, a diminutive placental from the late Eocene of Egypt

Seiffert

Simons

2000

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

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The lower dentition of Widanelfarasia (new genus), a diminutive late Eocene placental from the Fayum Depression in Egypt, is described. Widanelfarasia exhibits a complex of features associated with incipient zalambdodonty and at least three unequivocal apomorphies [loss of P 1, an enlarged I2 (relative to I3), and a basal cusp on I 2], which provide weak support for its placement as a possible sister taxon of either a tenrecid-chrysochlorid clade or of solenodontids. The former hypothesis gains additional support from biogeographical evidence, but both scenarios are currently tenuous as Widanelfarasia is clearly not truly zalambdodont. Phylogenetic hypotheses positing affinities with tenrecids alone or chrysochlorids alone must invoke either convergent acquisition of zalambdodonty in these taxa or autapomorphic reversal in Widanelfarasia. Given these considerations, a relationship with more generalized taxa from the Laurasian Paleogene (e.g., geolabidids, nyctitheriids, leptictids) cannot yet be ruled out. Comparisons with other Paleogene Afro-Arabian forms are generally inconclusive. A relationship with the earlier Eocene Chambilestes from Tunisia-currently represented by a single specimen preserving P 4 -M 3 -seems possible based on the geometry and predicted occlusal relationships of these teeth, but cannot be confidently determined until these two taxa come to be represented by common diagnostic elements. Todralestes (late Paleocene, Morocco) exhibits general phenetic similarities to Widanelfarasia, but it is not yet known whether this taxon shares any of Widanelfarasia's unequivocal dental apomorphies. Pending the recovery of more informative material, we tentatively refer Widanelfarasia to Placentalia incertae sedis. Truly zalambdodont placentals remain conspicuously absent from the Paleogene of Afro-Arabia.

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Epipubic bones in eutherian mammals from the Late Cretaceous of Mongolia

Cited by 110 publications

References 16 publications

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

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

The evolution of milk secretion and its ancient origins

Widanelfarasia, a diminutive placental from the late Eocene of Egypt

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