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Santiago Hernández Del Pino - One of the best experts on this subject based on the ideXlab platform.
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Caudal cranium of Thylacosmilus atrox (Mammalia, Metatheria, Sparassodonta), a South American predaceous sabertooth /
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
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caudal cranium of thylacosmilus atrox mammalia metatheria sparassodonta a south american predaceous sabertooth
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
Jin Meng - One of the best experts on this subject based on the ideXlab platform.
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Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals
National Science Review, 2020Co-Authors: Fangyuan Mao, Cunyu Liu, Morgan Hill Chase, Andrew K. Smith, Jin MengAbstract:Abstract We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the Ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.
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A comparative study on auditory and hyoid bones of Jurassic euharamiyidans and contrasting evidence for mammalian middle ear evolution
Journal of anatomy, 2019Co-Authors: Jin Meng, Xiaoting Zheng, Xiaoli Wang, Fangyuan Mao, Gang Han, Yuanqing WangAbstract:The holotypes of euharamiyidan Arboroharamiya allinhopsoni and Arboroharamiya jenkinsi preserve the auditory and hyoid bones, respectively. With additional structures revealed by micro-computerized tomography (CT) and X-ray micro-computed laminography (CL), we provide a detailed description of these minuscule bones. The stapes in the two species of Arboroharamiya are similar in having a strong process for insertion of the stapedius muscle. The incus is similar in having an almond-shaped body and a slim short process, in addition to a robust stapedial process with a short lenticular process preserved in A. allinhopsoni. The plate-like Ectotympanic in the two species of Arboroharamiya is similar and comparable to that of Qishou jizantang. The surangular in the two species has a fan-shaped body and a needle-shaped anterior process. The malleus, Ectotympanic, and surangular are fully detached from the dentary and should have functioned exclusively for hearing. All the auditory bones of Arboroharamiya display unique features unknown in other mammaliaforms. Moreover, hyoid elements are found in the two species of Arboroharamiya and co-exist with the five auditory bones in the holotype of A. allinhopsoni. The element interpreted as the stylohyal is similar to the bone identified as the Ectotympanic in Vilevolodon. We reconstruct the auditory apparatus of Arboroharamiya and compare it with that of Vilevolodon as well as those in extant mammals and basal mammaliaforms. The comparison shows diverse morphological patterns of the auditory region in mammaliaforms. In particular, those of Vilevolodon and Arboroharamiya differ significantly: the former has a mandibular middle ear, whereas the latter possesses a definitive mammalian middle ear. It is puzzling that the two sympatric and dentally similar taxa have such different auditory apparatuses. In light of the available evidence, we argue that the mandibular middle ear reconstructed in Vilevolodon encounters many problems, and the so-called Ectotympanic in Vilevolodon may be interpreted as a stylohyal; thus, the dilemma can be resolved.
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a jurassic gliding euharamiyidan mammal with an ear of five auditory bones
Nature, 2017Co-Authors: Gang Han, Fangyuan Mao, Yuanqing Wang, Jin MengAbstract:Gliding is a distinctive locomotion type that has been identified in only three mammal species from the Mesozoic era. Here we describe another Jurassic glider that belongs to the euharamiyidan mammals and shows hair details on its gliding membrane that are highly similar to those of extant gliding mammals. This species possesses a five-boned auditory apparatus consisting of the stapes, incus, malleus, Ectotympanic and surangular, representing, to our knowledge, the earliest known definitive mammalian middle ear. The surangular has not been previously identified in any mammalian middle ear, and the morphology of each auditory bone differs from those of known mammals and their kin. We conclude that gliding locomotion was probably common in euharamiyidans, which lends support to idea that there was a major adaptive radiation of mammals in the mid-Jurassic period. The acquisition of the auditory bones in euharamiyidans was related to the formation of the dentary-squamosal jaw joint, which allows a posterior chewing movement, and must have evolved independently from the middle ear structures of monotremes and therian mammals.
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Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont
Nature, 2011Co-Authors: Jin Meng, Yuanqing WangAbstract:The transference of post-dentary jaw elements to the cranium of mammals as auditory ossicles is one of the central topics in evolutionary biology of vertebrates. Homologies of these bones among jawed vertebrates have long been demonstrated by developmental studies; but fossils illuminating this critical transference are sparse and often ambiguous. Here we report the first unambiguous Ectotympanic (angular), malleus (articular and prearticular) and incus (quadrate) of an Early Cretaceous eutriconodont mammal from the Jehol Biota, Liaoning, China. The Ectotympanic and malleus have lost their direct contact with the dentary bone but still connect the ossified Meckel's cartilage (OMC); we hypothesize that the OMC serves as a stabilizing mechanism bridging the dentary and the detached ossicles during mammalian evolution. This transitional mammalian middle ear narrows the morphological gap between the mandibular middle ear in basal mammaliaforms and the definitive mammalian middle ear (DMME) of extant mammals; it reveals complex changes contributing to the detachment of ear ossicles during mammalian evolution.
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Monotreme affinities and low-frequency hearing suggested by multituberculate ear
Nature, 1995Co-Authors: Jin Meng, André R. WyssAbstract:MULTITUBERCULATES are an extinct, dentally distinctive group of Mesozoic/early Cenozoic mammals of uncertain affinities1. We report here the discovery of a multituberculate Ectotympanic bone, associated with the malleus in original life position, from two exquisitely preserved auditory regions. This documents, to our knowledge for the first time, incorporation of the angular and prearticular bones (jaw components in non-mammalian tetrapods) into the middle ear of multituberculates, favouring the hypothesized single origin of the ossicular chain in mammals2,3. Morphology and orientation of these elements are strikingly similar to those of the extant egg-laying platypus and echidnas, suggesting a unique common ancestry of these forms4, an affiliation once generally discredited5–8 but regaining some recent support9,10. The structure of these new multituberculate auditory ossicles, in conjuction with a greatly inflated vestibule and an uncoiled cochlea, implies an ear inefficient for reception of high-frequency airborne vibrations but well suited for bone-conducted hearing.
Analía M. Forasiepi - One of the best experts on this subject based on the ideXlab platform.
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caudal cranium of thylacosmilus atrox mammalia metatheria sparassodonta a south american predaceous sabertooth
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
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Caudal cranium of Thylacosmilus atrox (Mammalia, Metatheria, Sparassodonta), a South American predaceous sabertooth /
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
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On the development of the chondrocranium and the histological anatomy of the head in perinatal stages of marsupial mammals
Zoological Letters, 2017Co-Authors: Marcelo R. Sánchez-villagra, Analía M. ForasiepiAbstract:An overview of the literature on the chondrocranium of marsupial mammals reveals a relative conservatism in shape and structures. We document the histological cranial anatomy of individuals representing Monodelphis domestica , Dromiciops gliroides , Perameles sp. and Macropus eugenii . The marsupial chondrocranium is generally characterized by the great breadth of the lamina basalis, absence of pila metoptica and large otic capsules. Its most anterior portion (cupula nasi anterior) is robust, and anterior to it there are well-developed tactile sensory structures, functionally important in the neonate. Investigations of ossification centers at and around the nasal septum are needed to trace the presence of certain bones (e.g., mesethmoid, parasphenoid) across marsupial taxa. In many adult marsupials, the tympanic floor is formed by at least three bones: alisphenoid (alisphenoid tympanic process), Ectotympanic and petrosal (rostral and caudal tympanic processes); the squamosal also contributes in some diprotodontians. The presence of an entotympanic in marsupials has not been convincingly demonstrated. The tubal element surrounding the auditory tube in most marsupials is fibrous connective tissue rather than cartilage; the latter is the case in most placentals recorded to date. However, we detected fibrocartilage in a late juvenile of Dromiciops , and a similar tissue has been reported for Tarsipes . Contradictory reports on the presence of the tegmen tympani can be found in the literature. We describe a small tegmen tympani in Macropus . Several heterochronic shifts in the timing of development of the chondocranium and associated structures (e.g., nerves, muscles) and in the ossification sequence have been interpreted as largely being influenced by functional requirements related to the altriciality of the newborn marsupial during early postnatal life. Comparative studies of chondocranial development of mammals can benefit from a solid phylogenetic framework, research on non-classical model organisms, and integration with imaging and sectional data derived from computer-tomography.
Ross D. E. Macphee - One of the best experts on this subject based on the ideXlab platform.
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Caudal cranium of Thylacosmilus atrox (Mammalia, Metatheria, Sparassodonta), a South American predaceous sabertooth /
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
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caudal cranium of thylacosmilus atrox mammalia metatheria sparassodonta a south american predaceous sabertooth
Bulletin of the American Museum of Natural History, 2019Co-Authors: Analía M. Forasiepi, Ross D. E. Macphee, Santiago Hernández Del PinoAbstract:The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and Ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped Ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged Ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
Gregg F. Gunnell - One of the best experts on this subject based on the ideXlab platform.
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New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys
Nature, 2010Co-Authors: Iyad S. Zalmout, William J. Sanders, Laura M. Maclatchy, Gregg F. Gunnell, Yahya A. Al-mufarreh, Mohammad A. Ali, Abdul-azziz H. Nasser, Abdu M. Al-masari, Salih A. Al-sobhi, Ayman O. NadhraAbstract:The fossil record of primates is sparse, and many gaps remain in our knowledge. One gap relates to the divergence within the catarrhines — the ancestors of hominoids (apes and humans) and Old World monkeys. The discovery of a previously unknown catarrhine in Saudi Arabia, dated to 29–28 million years ago, helps to fill in some details. This specimen shows very few catarrhine specializations, suggesting that the divergence between Old World monkeys and hominoids must have occurred after this date. The primate fossil record is uneven, and substantial gaps remain. One gap is the divergence of cercopithecoids (Old World monkeys) and hominoids (apes and humans) within Old World higher primates (Catarrhini). This event was previously thought to have occurred sometime during the early Oligocene–early Miocene interval in Afro-Arabia, but the discovery of a new stem catarrhine in western Saudi Arabia narrows that gap. The Saudi specimen, dated to the mid-Oligocene around 29 million to 28 million years ago, shows no crown catarrhine specializations other than the presence of a tubular Ectotympanic, suggesting that the divergence of Old World monkeys and apes happened after that date. The size of the cranium indicates a medium-sized primate, between 15 and 20 kilograms in body mass. It is widely understood that Hominoidea (apes and humans) and Cercopithecoidea (Old World monkeys) have a common ancestry as Catarrhini deeply rooted in Afro-Arabia^ 1 , 2 , 3 , 4 . The oldest stem Catarrhini in the fossil record are Propliopithecoidea, known from the late Eocene to early Oligocene epochs (roughly 35–30 Myr ago) of Egypt, Oman and possibly Angola^ 5 , 6 , 7 , 8 , 9 , 10 . Genome-based estimates for divergence of hominoids and cercopithecoids range into the early Oligocene^ 11 ; however, the mid-to-late Oligocene interval from 30 to 23 Myr ago has yielded little fossil evidence documenting the morphology of the last common ancestor of hominoids and cercopithecoids, the timing of their divergence, or the relationship of early stem and crown catarrhines. Here we describe the partial cranium of a new medium-sized (about 15–20 kg) fossil catarrhine, Saadanius hijazensis , dated to 29–28 Myr ago. Comparative anatomy and cladistic analysis shows that Saadanius is an advanced stem catarrhine close to the base of the hominoid–cercopithecoid clade. Saadanius is important for assessing competing hypotheses about the ancestral morphotype for crown catarrhines^ 1 , 12 , 13 , 14 , early catarrhine phylogeny^ 12 , 15 and the age of hominoid–cercopithecoid divergence^ 11 . Saadanius has a tubular Ectotympanic but lacks synapomorphies of either group of crown Catarrhini, and we infer that the hominoid–cercopithecoid split happened later, between 29–28 and 24 Myr ago.
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new oligocene primate from saudi arabia and the divergence of apes and old world monkeys
Nature, 2010Co-Authors: Iyad S. Zalmout, William J. Sanders, Laura M. Maclatchy, Gregg F. Gunnell, Mohammad A. Ali, Abdul-azziz H. Nasser, Yahya S A Almufarreh, Abdu M Almasari, Salih A Alsobhi, Ayman O. NadhraAbstract:It is widely understood that Hominoidea (apes and humans) and Cercopithecoidea (Old World monkeys) have a common ancestry as Catarrhini deeply rooted in Afro-Arabia. The oldest stem Catarrhini in the fossil record are Propliopithecoidea, known from the late Eocene to early Oligocene epochs (roughly 35-30 Myr ago) of Egypt, Oman and possibly Angola. Genome-based estimates for divergence of hominoids and cercopithecoids range into the early Oligocene; however, the mid-to-late Oligocene interval from 30 to 23 Myr ago has yielded little fossil evidence documenting the morphology of the last common ancestor of hominoids and cercopithecoids, the timing of their divergence, or the relationship of early stem and crown catarrhines. Here we describe the partial cranium of a new medium-sized (about 15-20 kg) fossil catarrhine, Saadanius hijazensis, dated to 29-28 Myr ago. Comparative anatomy and cladistic analysis shows that Saadanius is an advanced stem catarrhine close to the base of the hominoid-cercopithecoid clade. Saadanius is important for assessing competing hypotheses about the ancestral morphotype for crown catarrhines, early catarrhine phylogeny and the age of hominoid-cercopithecoid divergence. Saadanius has a tubular Ectotympanic but lacks synapomorphies of either group of crown Catarrhini, and we infer that the hominoid-cercopithecoid split happened later, between 29-28 and 24 Myr ago.
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New Notharctine (Primates, Adapiformes) Skull From the Uintan (Middle Eocene) of San Diego County, California
American journal of physical anthropology, 1995Co-Authors: Gregg F. GunnellAbstract:Californian primates, Cranial morphology, ABSTRACT A new genus and species of notharctine primate, Hespero- lemur actius, is described from Uintan (middle Eocene) aged rocks of San Diego County, California. Hesperolemur differs from all previously described adapiforms in having the anterior third of the Ectotympanic anulus fused to the internal lateral wall of the auditory bulla. In this feature Hesperolemur superficially resembles extant cheirogaleids. Hesperolemur also differs from previously known adapiforms in lacking bony canals that transmit the inter- nal carotid artery through the tympanic cavity. Hesperolemur, like the later occurring North American cercamoniine Mahgarita steuensi, appears to have lacked a stapedial artery. Evidence from newly discovered skulls ofNotharctus and Smilodectes, along with Hesperolemur, Mahgarita, and Adapis, indicates that the tympanic arterial circulatory pattern of these adapiforms is charac- terized by stapedial arteries that are smaller than promontory arteries, a feature shared with extant tarsiers and anthropoids and one of the character- istics often used to support the existence of a haplorhine-strepsirhine dichot- omy among extant primates. The existence of such a dichotomy among Eocene primates is not supported by any compelling evidence. Hesperolemur is the latest occurring notharctine primate known from North America and is the only notharctine represented among a relatively diverse primate fauna from southern California. The coastal lowlands of southern California presumably served as a refuge area for primates during the middle and later Eocene as climates deteriorated in the continental interior. Hesperolemur probably was an immigrant taxon that entered California from either the northern (Wyo- mingmtah) or southern (New Mexico) western interior during the middle Eocene o 1995 Wiley-Liss, Inc.
