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Gheerbrant E, Schmitt A, Billet G. Petrosal and bony labyrinth morphology of the stem paenungulate mammal (Paenungulatomorpha) Ocepeia daouiensis from the Paleocene of Morocco. J Anat 2022; 240:595-611. [PMID: 32735727 PMCID: PMC8930808 DOI: 10.1111/joa.13255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 05/25/2020] [Accepted: 05/25/2020] [Indexed: 11/29/2022] Open
Abstract
Based on high-resolution computed tomography, we describe in detail the petrosal and inner ear anatomy of one of the few known African stem paenungulates (Paenungulatomorpha), Ocepeia daouiensis from the Selandian of the Ouled Abdoun phosphate basin (Morocco). The petrosal of Ocepeia displays some remarkable, probably derived features (among eutherians) such as relatively small pars cochlearis, pars canalicularis labyrinth (including small semicircular canals), a large wing-like pars mastoidea, a large and inflated tegmen tympani, and the dorsoventral orientation of the large canal for the ramus superior. The presence of small semicircular canals in Ocepeia is an interesting shared trait with tenrecoidean afrotherians. Otherwise, and consistent with a general primitive skull morphology, the middle ear and labyrinth of Ocepeia daouiensis is characterised by many plesiomorphic traits close to the eutherian generalised plan. This adds to the rather generalised morphology of the earliest crown paenungulates such as Eritherium, Phosphatherium and Seggeurius to support an ancestral paenungulatomorph morphotype poorly derived from the eutherian pattern. As a result, Ocepeia provides key morphological and fossil data to test phylogenetic relationships of the Afrotheria (including Paenungulatomorpha) at the placental root mostly inferred from molecular studies.
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Affiliation(s)
- Emmanuel Gheerbrant
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
| | - Arnaud Schmitt
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
| | - Guillaume Billet
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
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Perini FA, Macrini TE, Flynn JJ, Bamba K, Ni X, Croft DA, Wyss AR. Comparative Endocranial Anatomy, Encephalization, and Phylogeny of Notoungulata (Placentalia, Mammalia). J MAMM EVOL 2021. [DOI: 10.1007/s10914-021-09583-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Shelley SL, Bertrand OC, Brusatte SL, Williamson TE. Petrosal Anatomy of the Paleocene Eutherian Mammal Deltatherium fundaminis (Cope, 1881). J MAMM EVOL 2021; 28:1161-1180. [PMID: 34483638 PMCID: PMC8406390 DOI: 10.1007/s10914-021-09568-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2021] [Indexed: 12/04/2022]
Abstract
We describe the tympanic anatomy of the petrosal of Deltatherium fundaminis, an enigmatic Paleocene mammal based on cranial specimens recovered from New Mexico, U.S.A. Although the ear region of Deltatherium has previously been described, there has not been a comprehensive, well-illustrated contribution using current anatomical terminology. The dental and cranial anatomy of Deltatherium is a chimera, with morphological similarities to both ‘condylarth’ and ‘cimolestan’ taxa. As such, the phylogenetic relationships of this taxon have remained elusive since its discovery, and it has variably been associated with Arctocyonidae, Pantodonta and Tillodontia. The petrosal of Deltatherium is anteriorly bordered by an open space comprising a contiguous carotid opening and pyriform fenestra. The promontorium features both a small rostral tympanic process and small epitympanic wing but lacks well-marked sulci. A large ventral facing external aperture of the canaliculus cochleae is present and bordered posteriorly by a well-developed caudal tympanic process. The hiatus Fallopii opens on the ventral surface of the petrosal. The tegmen tympani is mediolaterally broad and anteriorly expanded, and its anterior margin is perforated by a foramen for the ramus superior of the stapedial artery. The tympanohyal is small but approximates the caudal tympanic process to nearly enclose the stylomastoid notch. The mastoid is widely exposed on the basicranium and bears an enlarged mastoid process, separate from the paraoccipital process. These new observations provide novel anatomical data corroborating previous hypotheses regarding the plesiomorphic eutherian condition but also reveal subtle differences among Paleocene eutherians that have the potential to help inform the phylogeny of Deltatherium.
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Affiliation(s)
- Sarah L Shelley
- School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom.,Carnegie Museum of Natural History, Pittsburgh, Pennsylvania United States of America
| | - Ornella C Bertrand
- School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom.,New Mexico Museum of Natural History and Science, Albuquerque, New Mexico United States of America
| | - Thomas E Williamson
- New Mexico Museum of Natural History and Science, Albuquerque, New Mexico United States of America
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Mao F, Hu Y, Li C, Wang Y, Chase MH, Smith AK, Meng J. Integrated hearing and chewing modules decoupled in a Cretaceous stem therian mammal. Science 2019; 367:305-308. [PMID: 31806694 DOI: 10.1126/science.aay9220] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022]
Abstract
On the basis of multiple skeletal specimens from Liaoning, China, we report a new genus and species of Cretaceous stem therian mammal that displays decoupling of hearing and chewing apparatuses and functions. The auditory bones, including the surangular, have no bone contact with the ossified Meckel's cartilage; the latter is loosely lodged on the medial rear of the dentary. This configuration probably represents the initial morphological stage of the definitive mammalian middle ear. Evidence shows that hearing and chewing apparatuses have evolved in a modular fashion. Starting as an integrated complex in non-mammaliaform cynodonts, the two modules, regulated by similar developmental and genetic mechanisms, eventually decoupled during the evolution of mammals, allowing further improvement for more efficient hearing and mastication.
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Affiliation(s)
- Fangyuan Mao
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China. .,CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China.,Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA
| | - Yaoming Hu
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Chuankui Li
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.,CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
| | - Yuanqing Wang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.,CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
| | - Morgan Hill Chase
- Microscopy and Imaging Facility, American Museum of Natural History, New York, NY 10024, USA
| | - Andrew K Smith
- Microscopy and Imaging Facility, American Museum of Natural History, New York, NY 10024, USA
| | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA. .,Earth and Environmental Sciences, Graduate Center, City University of New York, New York, NY 10016, USA
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Bertrand OC, Shelley SL, Wible JR, Williamson TE, Holbrook LT, Chester SGB, Butler IB, Brusatte SL. Virtual endocranial and inner ear endocasts of the Paleocene 'condylarth' Chriacus: new insight into the neurosensory system and evolution of early placental mammals. J Anat 2019; 236:21-49. [PMID: 31667836 DOI: 10.1111/joa.13084] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2019] [Indexed: 02/06/2023] Open
Abstract
The end-Cretaceous mass extinction allowed placental mammals to diversify ecologically and taxonomically as they filled ecological niches once occupied by non-avian dinosaurs and more basal mammals. Little is known, however, about how the neurosensory systems of mammals changed after the extinction, and what role these systems played in mammalian diversification. We here use high-resolution computed tomography (CT) scanning to describe the endocranial and inner ear endocasts of two species, Chriacus pelvidens and Chriacus baldwini, which belong to a cluster of 'archaic' placental mammals called 'arctocyonid condylarths' that thrived during the ca. 10 million years after the extinction (the Paleocene Epoch), but whose relationships to extant placentals are poorly understood. The endocasts provide new insight into the paleobiology of the long-mysterious 'arctocyonids', and suggest that Chriacus was an animal with an encephalization quotient (EQ) range of 0.12-0.41, which probably relied more on its sense of smell than vision, because the olfactory bulbs are proportionally large but the neocortex and petrosal lobules are less developed. Agility scores, estimated from the dimensions of the semicircular canals of the inner ear, indicate that Chriacus was slow to moderately agile, and its hearing capabilities, estimated from cochlear dimensions, suggest similarities with the extant aardvark. Chriacus shares many brain features with other Paleocene mammals, such as a small lissencephalic brain, large olfactory bulbs and small petrosal lobules, which are likely plesiomorphic for Placentalia. The inner ear of Chriacus also shares derived characteristics of the elliptical and spherical recesses with extinct species that belong to Euungulata, the extant placental group that includes artiodactyls and perissodactyls. This lends key evidence to the hypothesized close relationship between Chriacus and the extant ungulate groups, and demonstrates that neurosensory features can provide important insight into both the paleobiology and relationships of early placental mammals.
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Affiliation(s)
- Ornella C Bertrand
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Sarah L Shelley
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | - John R Wible
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | | | - Luke T Holbrook
- Department of Biological Sciences, Rowan University, Glassboro, NJ, USA
| | - Stephen G B Chester
- Department of Anthropology and Archaeology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Department of Anthropology, The Graduate Center, City University of New York, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - Ian B Butler
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK.,New Mexico Museum of Natural History and Science, Albuquerque, NM, USA
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Harper T, Rougier GW. Petrosal morphology and cochlear function in Mesozoic stem therians. PLoS One 2019; 14:e0209457. [PMID: 31412094 PMCID: PMC6693738 DOI: 10.1371/journal.pone.0209457] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 06/07/2019] [Indexed: 11/19/2022] Open
Abstract
Here we describe the bony anatomy of the inner ear and surrounding structures seen in three plesiomorphic crown mammalian petrosal specimens. Our study sample includes the triconodont Priacodon fruitaensis from the Upper Jurassic of North America, and two isolated stem therian petrosal specimens colloquially known as the Höövör petrosals, recovered from Aptian-Albian sediments in Mongolia. The second Höövör petrosal is here described at length for the first time. All three of these petrosals and a comparative sample of extant mammalian taxa have been imaged using micro-CT, allowing for detailed anatomical descriptions of the osteological correlates of functionally significant neurovascular features, especially along the abneural wall of the cochlear canal. The high resolution imaging provided here clarifies several hypotheses regarding the mosaic evolution of features of the cochlear endocast in early mammals. In particular, these images demonstrate that the membranous cochlear duct adhered to the bony cochlear canal abneurally to a secondary bony lamina before the appearance of an opposing primary bony lamina or tractus foraminosus. Additionally, while corroborating the general trend of reduction of venous sinuses and plexuses within the pars cochlearis seen in crownward mammaliaforms generally, the Höövör petrosals show the localized enlargement of a portion of the intrapetrosal venous plexus. This new vascular feature is here interpreted as the bony accommodation for the vein of cochlear aqueduct, a structure that is solely, or predominantly, responsible for the venous drainage of the cochlear apparatus in extant therians. Given that our fossil stem therian inner ear specimens appear to have very limited high-frequency capabilities, the development of these modern vascular features of the cochlear endocast suggest that neither the initiation or enlargement of the stria vascularis (a unique mammalian organ) was originally associated with the capacity for high-frequency hearing or precise sound-source localization.
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Affiliation(s)
- Tony Harper
- Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Guillermo W. Rougier
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky, United States of America
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Cameron J, Shelley SL, Williamson TE, Brusatte SL. The Brain and Inner Ear of the Early Paleocene “Condylarth”
Carsioptychus coarctatus
: Implications for Early Placental Mammal Neurosensory Biology and Behavior. Anat Rec (Hoboken) 2018; 302:306-324. [DOI: 10.1002/ar.23903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 04/04/2018] [Accepted: 04/16/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Joe Cameron
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
| | - Sarah L. Shelley
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
| | | | - Stephen L. Brusatte
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
- New Mexico Museum of Natural History and Science Albuquerque New Mexico
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Phylogenetic and functional implications of the ear region anatomy of Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina. Naturwissenschaften 2018; 105:28. [DOI: 10.1007/s00114-018-1548-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 02/21/2018] [Accepted: 02/23/2018] [Indexed: 01/26/2023]
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A Digital Endocranial Cast of the Early Paleocene (Puercan) 'Archaic' Mammal Onychodectes tisonensis (Eutheria: Taeniodonta). J MAMM EVOL 2017; 25:179-195. [PMID: 29755252 PMCID: PMC5938319 DOI: 10.1007/s10914-017-9381-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Eutherian mammals-placentals and their closest extinct relatives-underwent a major radiation following the end-Cretaceous extinction, during which they evolved disparate anatomy and established new terrestrial ecosystems. Much about the timing, pace, and causes of this radiation remain unclear, in large part because we still know very little about the anatomy, phylogenetic relationships, and biology of the so-called 'archaic' eutherians that prospered during the ~10 million years after the extinction. We describe the first digital endocranial cast of a taeniodont, a bizarre group of eutherians that flourished in the early Paleogene, reconstructed from a computed tomography (CT) scan of a late Puercan (65.4 million year old) specimen of Onychodectes tisonensis that recovered most of the forebrain and midbrain and portions of the inner ear. Notable features of the endocast include long, broad olfactory bulbs, dorsally-positioned rhinal fissures, and a lissencephalic cerebrum. Comparison with other taxa shows that Onychodectes possessed some of the largest olfactory bulbs (relative to cerebral size) of any known mammal. Statistical analysis of modern mammals shows that relative olfactory bulb dimensions are not strongly correlated with body size or fossorial digging for shelter, but relative bulb width is significantly greater in taxa that habitually dig to forage for food. The anatomical description and statistical results allow us to present an ecological model for Onychodectes and similar taeniodonts, in which they are animals of simple behavior that rely on a strong sense of smell to locate buried food before extracting and processing it with their specialized skeletal anatomy.
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Costeur L, Mennecart B, Müller B, Schulz G. Prenatal growth stages show the development of the ruminant bony labyrinth and petrosal bone. J Anat 2016; 230:347-353. [PMID: 27726136 DOI: 10.1111/joa.12549] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2016] [Indexed: 12/29/2022] Open
Abstract
Foetuses are a source of scientific information to understand the development and evolution of anatomical structures. The bony labyrinth, surrounding the organ of balance and hearing, is a phylogenetically and ecologically informative structure for which still little concerning growth and shape variability is known in many groups of vertebrates. Except in humans, it is poorly known in many other placentals and its prenatal growth has almost never been studied. Ruminants are a diversified group of placentals and represent an interesting case study to understand the prenatal growth of the ear region. We computed tomography -scanned five cow foetuses and an adult petrosal bone (Bos taurus, Artiodactyla, Mammalia), and describe the bony labyrinth when already ossified. The foetuses encompass the second half of the 9.3-month-long gestation period of the cow. They were sampled at different ontogenetic stages to understand how and when the petrosal bone and bony labyrinth ossify in ruminants. The petrosal bone and bony labyrinth ossify within about 20 days in the fourth month of gestation. The bony labyrinth is already fully ossified at least in the 6th month, while only the cochlea, most of the vestibule and the common crus are already ossified at the beginning of the 4th month. The pars canalicularis of the petrosal thus ossifies at last. The size and volume of the bony labyrinth stay similar from the 6th month (possibly even from the 5th). From the end of the 4th month of gestation, a progressive lengthening of the cochlear aqueduct and endolymphatic sac occurs, culminating in the adult form and partly explaining the larger volume of the later. The inner ear in the cow ossifies quickly during the gestation period, being fully ossified around mid-gestation time, as in humans. The adult size and most of its volume are reached by mid-gestation time while the petrosal bone and skull still grow. A negative ontogenetic allometry between the bony labyrinth and the petrosal bone and skull is thus observed. It matches the evolutionary negative allometry of the structure observed in earlier studies. Few changes occur after ossification is achieved; only open structures (i.e. cochlear aqueduct and endolymphatic sac) continue to grow after birth and reflect size increase of the petrosal bone.
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Affiliation(s)
- Loïc Costeur
- Naturhistorisches Museum Basel, Basel, Switzerland
| | | | - Bert Müller
- Biomaterials Science Center, University of Basel, c/o University Hospital Basel, Basel, Switzerland
| | - Georg Schulz
- Biomaterials Science Center, University of Basel, c/o University Hospital Basel, Basel, Switzerland
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