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1.
J?rg Fr?bisch Robert R. Reisz 《Proceedings. Biological sciences / The Royal Society》2009,276(1673):3611-3618
Vertebrates have repeatedly filled and partitioned the terrestrial ecosystem, and have been able to occupy new, previously unexplored habitats throughout their history on land. The arboreal ecospace is particularly important in vertebrate evolution because it provides new food resources and protection from large ground-dwelling predators. We investigated the skeletal anatomy of the Late Permian (approx. 260 Ma) herbivorous synapsid Suminia getmanovi and performed a morphometric analysis of the phalangeal proportions of a great variety of extant and extinct terrestrial and arboreal tetrapods to discern locomotor function and habitat preference in fossil taxa, with special reference to Suminia. The postcranial anatomy of Suminia provides the earliest skeletal evidence for prehensile abilities and arboreality in vertebrates, as indicated by its elongate limbs, intrinsic phalangeal proportions, a divergent first digit and potentially prehensile tail. The morphometric analysis further suggests a differentiation between grasping and clinging morphotypes among arboreal vertebrates, the former displaying elongated proximal phalanges and the latter showing an elongation of the penultimate phalanges. The fossil assemblage that includes Suminia demonstrates that arboreality and resource partitioning occurred shortly after the initial establishment of the modern type of terrestrial vertebrate ecosystems, with a large number of primary consumers and few top predators. 相似文献
2.
《Journal of morphology》2017,278(8):1020-1032
Most nonmammalian synapsids possess a mid‐dorsal depression in the brain cavity known as the “unossified zone.” It remains obscure which structures this zone contained, and, as candidates, the vermis of the cerebellum, the superior sagittal sinus, a junction of several blood vessels, the pineal gland or other midbrain structures were considered. Neutron tomography of a skull of Diictodon feliceps (Therapsida, Anomodontia) revealed some clear impressions of canals in this region of the brain cavity. Furthermore, the prootic sinus probably ran on the internal surface of the pila antotica and had a similar course in anomodonts as it has been proposed for cynodonts and Mesozoic mammals. Comparisons with the vascular systems of nonmammalian synapsids and mammals suggest that the unossified zone is best interpreted as a terminal chamber of the anterior segment of the medial head vein, which housed the junction of the superior sagittal sinus and the transverse sinuses. Consequently, the system of cranial vessels in Diictodon reveals a partial division of the medial head vein system into an anterior and a posterior segment at an early stage of synapsid evolution, which is consistent with the well‐known common pattern of early ontogenetic development in amniotes. J. Morphol., 2017. © 2017 Wiley Periodicals, Inc. 相似文献
3.
The locomotion of primates differs from that of other mammals in three fundamental ways. During quadrupedal walking, primates use diagonal sequence gaits, protract their arms more at forelimb touchdown, and experience lower vertical substrate reaction forces on their forelimbs relative to their hindlimbs. It is widely held that the unusual walking gaits of primates represent a basal adaptation for movement on thin, flexible branches and reflect a major change in the functional role of the forelimb. However, little data on nonprimate arboreal mammals exist to test this notion. To that end, we examined the gait mechanics of the woolly opossum (Caluromys philander), a marsupial convergent with small-bodied prosimians in ecology, behavior, and morphology. Data on the footfall sequence, relative arm protraction, and peak vertical substrate reaction forces were obtained from videotapes and force records for three adult woolly opossums walking quadrupedally on a wooden runway and a thin pole. For all steps recorded on both substrates, woolly opossums always used diagonal sequence walking gaits, protracted their arms beyond 90 degrees relative to horizontal body axis, and experienced peak vertical substrate reaction forces on forelimbs that were significantly lower than on hindlimbs. The woolly opossum is the first nonprimate mammal to show locomotor mechanics that are identical to those of primates. This case of convergence between primates and a committed fine-branch, arboreal marsupial strongly implies that the earliest primates evolved gait specializations for fine-branch locomotion, which reflect important changes in forelimb function. 相似文献
4.
Current phylogenetic hypotheses for the dicynodonts conflict, probably because the characters used, especially those of the jaws and facial region, show considerable convergence. Characters of the braincase and basipterygoid articulation of the Late Permian–Middle Triassic dicynodonts Diictodon , Dicynodon , Kingoria, Lystrosaurus , Rechnisaurus , and 14 other genera, may have phylogenetic value. Parsimony analysis and the character compatability permutation test suggest, at the highest possible confidence level, that the data set contains significant hierarchical structure, interpreted as a result of phylogeny. The most parsimonious tree broadly agrees with all recent hypotheses on the relationships among dicynodonts. However, it conflicts with the recent suggestion that Lystrosaurus is part of a clade of Middle–Late Triassic dicynodonts, but supports the basal position of Kingoria . The use of Eodicynodon as an outgroup does not perturb the parsimonious relationship of the included taxa. Topological constraints reveal that phylogenetic hypotheses based only on basicranial characters are not robust. Characters of the basipterygoid articulation and inner braincase have high consistency and retention indices, which suggests that the main evolutionary transformations in the dicynodont basicranium occurred within these structures. 相似文献
5.
T. S. KEMP 《Zoological Journal of the Linnean Society》2006,147(4):473-488
Several mutually incompatible theories exist about how and why endothermy evolved in mammals and birds. Some take the primary function to have been thermoregulation, selected for one adaptive purpose or another. Others take the high aerobic metabolic rate to have been primary. None of these theories is incontrovertibly supported by evidence, either from the fossil record of the synapsid amniotes or from observations and experiments on modern organisms. Furthermore, all are underpinned by the tacit assumption that endothermy must have evolved in a stepwise pattern, with an initial adaptive function followed only later by the addition of further functions. It is argued that this assumption is unrealistic and that the evolution of endothermy can be explained by the correlated progression model. Each structure and function associated with endothermy evolved a small increment at a time, in loose linkage with all the others evolving similarly. The result is that the sequence of organisms maintained functional integration throughout, and no one of the functions of endothermy was ever paramount over the others. The correlated progression model is tested by the nature of the integration between the parts as seen in living mammals, by computer simulations of the evolution of complex, multifunctional, multifactorial biological systems, and by reference to the synapsid fossil record, which is fully compatible with the model. There are several potentially important implications to be drawn from this example concerning the study of the evolution of complex structure and the new higher taxa that manifest it. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 147 , 473–488. 相似文献
6.
Jun Liu Bruce Rubidge Jinling Li 《Proceedings. Biological sciences / The Royal Society》2010,277(1679):285-292
A new well-preserved basal therapsid skull from the Xidagou Formation, Middle Permian of China, is identified as Biseridens qilianicus. The following synapomorphies distinguish Biseridens as an anomodont and not an eotitanosuchian as previously described: short snout; dorsally elevated zygomatic arch and septomaxilla lacking elongated posterodorsal process between nasal and maxilla. The presence of a differentiated tooth row; denticles on vomer, palatine and pterygoid; contact between tabular and opisthotic; lateral process of transverse flange of pterygoid free of posterior ramus and absence of mandibular foramen exclude it from other anomodonts. Our cladistic analysis indicates Biseridens to be the most basal anomodont, highlights separate Laurasian and Gondwanan basal anomodont clades and suggests that dicynodonts had their origins in the Gondwanan clade. The co-occurrence of the most basal anomodont (Biseridens) together with the most basal therapsid (Raranimus), basal anteosaurid dinocephalians, bolosaurids and dissorophids suggests that the earliest therapsid faunas are from China. 相似文献
7.
The palate and partial braincase of the holotype of Dimetrodon milleri (MCZ 1365) are preserved in three dimensions, but have yet to be described in detail. Here, we describe these structures for the first time for this species, and compare them with the better-known specimens of D. limbatus. Interesting characteristics of the morphology include the patterns of articulation of the palatal elements, including the palatine and vomer, and anatomy of the pterygoid in the posterior region of the palatal vacuities. Dimetrodon milleri is found to differ from D. limbatus in the lack of teeth on the ectopterygoid, the shape of the basal process of the epipterygoid, and the anterior extent of the palatine and pterygoid. The two species are similar in the relative position of the basicranial articulation, but differ significantly from that in other sphenacodontids, including Secodontosaurus and Sphenacodon. The evolution of these cranial features will be the subject of future phylogenetic analyses of sphenacodontids. 相似文献
8.
AbstractAnalytical palaeohistology techniques have allowed a better understanding of the microstructure of fossil bone, as well as of bone pathologies of extinct animals. Osteomyelitis is one of the oldest identified bone pathologies, occurring in Synapsida dating back as far as the Lower Permian. Here we show the presence of this pathology in the femur of Jonkeria parva, an omnivorous titanosuchid from the Tapinocephalus Assemblage Zone of the Karoo Basin of South Africa. The pathology is characterised by bony radial spicules growing perpendicular to the normal orientation of the unaffected fibrolamellar bone tissue, and shows localised increase in vascular canal size. Puncture marks on the femur suggests that an attack by a predator may have resulted in a bacterial infection that caused contiguous and subjacent osteomyelitis. 相似文献
9.
G. M. KING B. W. OELOFSEN B. S. RUBIDGE 《Zoological Journal of the Linnean Society》1989,96(2):185-211
The skull structure of dicynodonts may be regarded as a complex adaptation towards herbivorous feeding. The present work examines how and why this adaptation may have evolved. A cladogram of the dicynodonts is presented and from it a sequence of hypothetical ancestral forms is inferred. The jaw musculature of dicynodonts and other therapsids is described and in particular the early dicynodont Eodicynodon oosthuizeni is described in detail. This information is used to draw up a sequence of ancestral stages whose basic skull anatomy, jaw muscle organization and masticatory properties are described. Differences in masticatory properties between these stages are pinpointed and an explanation to account for the development of these differences is advanced. It is concluded that the changes in skull organization seen during the evolution of dicynodonts are consistent with the hypothesis that a propalinal jaw action was being improved by selection, and that this was required to permit dicynodonts to be efficient herbivores. 相似文献
10.
C. BARRY COX 《Zoological Journal of the Linnean Society》1998,122(1-2):349-384
The structure and functioning of the dicynodont jaw system are described. A pivoting action of the lower jaw around the palate posteromedian to the caniniform processes is as basic to the jaw movement as is the well-known double-convex jaw articulation. The sequence of origin of the characteristic features of the dicynodonts is analysed cladistically; this demonstrates the patterns of association of these characters into functional character-complexes. The structures of the palate and lower jaw, and their functional integration in feeding, are described and illustrated in standard format. Five different lineages of dicynodont can be identified: Eodicynodon; the robertoids (including Diictodon ); the dicynodontoids (including Dicynodon and the majority of the large dicynodont genera of the Permian and Triassic); the endothiodontoids (including Prodicynodon [='Chelydontops'] and Pristerodon ), and the emydopoids (including Cistecephalus, Myosaurus and Kingoria ). Eodicynodon or a similar form could have been ancestral to the other four lineages. The robertoids probably fed upon the stems and rhizomes of equisetaleans, while the varied dicynodontoids probably fed upon the varied glossopterid seed-ferns. The endothiodontoids, too, were probably herbivorous, but many, perhaps all, of the small emydopoids were burrowing and may have been omnivorous. The dicynodonts were probably ectothermal, and the dicynodontoids may have migrated to warmer latitudes in the winter. Only c. 20 genera of Karoo dicynodont are now recognized as valid, and it is suggested that this fauna is now almost completely known. Their distribution in the Karoo biozones is reviewed and correlated with environmental changes. The Permian ancestors of the Triassic dicynodonts, including Lystrosaurus , probably lived on higher, drier ground, and were therefore already adapted to the more fibrous food that spread into the basins as the climate became drier in the Triassic. 相似文献
11.
12.
The basal clade Burnetiamorpha is known from only two specimens representing two genera, Proburnetia from the Severodvinskian horizon of the Vyatka River Basin in the Kotelnich district of Russia, and Burnetia from the Dicynodon Assemblage Zone of the Beaufort Group of South Africa. Both genera are of Late Tatarian (Late Permian) age. This paper describes the cranial morphology of a new genus of burnetiamorph, Bullacephalus , from the Late Permian Tapinocephalus Assemblage Zone of the Beaufort Group of South Africa. It is known from a relatively complete skull and lower jaw and is the best preserved burnetiamorph yet discovered. Apart from being the oldest member of the clade, Bullacephalus is also morphologically the least derived and provides new evidence on the phylogeny of this poorly understood group of basal therapsids. 相似文献
13.
《Journal of morphology》2017,278(8):1033-1057
The special sensory, motor, and cognitive capabilities of mammals mainly depend upon the neocortex, which is the six‐layered cover of the mammalian forebrain. The origin of the neocortex is still controversial and the current view is that larger brains with neocortex first evolved in late Triassic Mammaliaformes. Here, we report the earliest evidence of a structure analogous to the mammalian neocortex in a forerunner of mammals, the fossorial anomodont Kawingasaurus fossilis from the late Permian of Tanzania. The endocranial cavity of Kawingasaurus is almost completely ossified, which allowed a less hypothetical virtual reconstruction of the brain endocast to be generated. A parietal foramen is absent. A small pit between the cerebral hemispheres is interpreted as a pineal body. The inflated cerebral hemispheres are demarcated from each other by a median sulcus and by a possible rhinal fissure from the rest of the endocast. The encephalization quotient estimated by using the method of Eisenberg is 0.52, which is 2–3 times larger than in other nonmammalian synapsids. Another remarkable feature are the extremely ramified infraorbital canals in the snout. The shape of the brain endocast, the extremely ramified maxillary canals as well as the small frontally placed eyes suggest that special sensory adaptations to the subterranean habitat such as a well developed sense of touch and binocular vision may have driven the parallel evolution of an equivalent of the mammalian neocortex and a mammal‐like lemnothalamic visual system in Kawingasaurus . The gross anatomy of the brain endocast of Kawingasaurus supports the Outgroup Hypothesis, according to which the neocortex evolved from the dorsal pallium of an amphibian‐like ancestor, which receives sensory projections from the lemnothalamic pathway. The enlarged brain as well as the absence of a parietal foramen may be an indication for a higher metabolic rate of Kawingasaurus compared to other nonmammalian synapsids. 相似文献
14.
Patranomodon nyaphulii , known from a nearly complete skull, lower jaw and partial postcranial skeleton, is morphologically the most primitive anomodont therapsid yet discovered. It is from the Eodicynodon Assemblage Zone, the lowest biozone of the Beaufort Group of South Africa, which has a primitive therapsid fauna comparable with that of the Russian Zone I. Patranaomodon is primitive with respect to other anomodonts in having short palatal exposure of the premaxilla, an unreduced tabular, a slit-like interpterygoidal vacuity, a screw-shaped jaw articulation (which precludes fore-aft sliding of the lower jaw), and only three sacral vertebrae. The poorly-known Galechirus and Galepus from the younger Cistecephalus Assemblage Zone appear to be at a comparably primitive evolutionary grade, and the three genera are tentatively united in the family Galechiridae. The taxon Dromasauria is shown to be paraphyletic and therefore should be discarded. 相似文献
15.
Abstract: Early Permian terrestrial vertebrate faunal assemblages of Laurasia are dominated by large ophiacodontid, sphenacodontid, and edaphosaurid synapsids. This pattern contrasts with the fauna recovered from the Early Permian fissure fill deposits near Richards Spur, Oklahoma, where derived nontherapsid synapsids are rare. The fragmentary remains of Thrausmosaurus serratidens constitute the only published report of Sphenacodontidae from this locality. Here, we re-evaluate T. serratidens in light of new information on the faunal assemblage of this locality. We confirm that the type material of T. serratidens cannot be assigned to Sphenacodontidae and conclude that it pertains to an indeterminate varanopid. We also describe new material, including a partial maxilla, several isolated jaw fragments with teeth, an isolated precaniniform tooth and a posterior cervical vertebra that represents unequivocal sphenacodontid remains from the Richards Spur assemblage. This material is the first definitive record of a eupelycosaurian synapsid other than a varanopid from this important locality. Faunal similarities between Richards Spur and the Bromacker Quarry, Germany, may be reflective of upland terrestrial communities during the Early Permian. 相似文献
16.
Michael Laaß 《Journal of morphology》2015,276(9):1089-1099
The cranial endocast of Pristerodon mackayi is described, which has been virtually reconstructed on the basis of neutron tomographic data. The gross anatomy of the cranial endocast of Pristerodon resembles other nonmammalian synapsids such as Thrinaxodon liorhinus in having a narrow, tubular forebrain, well developed olfactory bulbs, a large parietal foramen and unossified zone. As it is the case in cynodonts the hindbrain of Pristerodon is broader than the mid‐ and forebrain. Large paraflocculi are developed. The medulla oblongata can be well distinguished from the pons. The pons is divided by a median ridge into two portions. There is no evidence for a neocortex, which seems to be also reflected in the low encephalization quotient of 0.18 estimated according to the method of Eisenberg. J. Morphol. 276:1089–1099, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
17.
Fossilised traces of swimming amphibians, assigned to Batrachichnus delicatulus and Serpentichnus robledoensis igen. et isp. nov., are described from the Lower Permian of the Robledo Mountains, southern New Mexico. The B. delicatulus specimen is interpreted as a trackway of a small 'amphibian' (temnospondyl, nectridean, microsaur or juvenile embolomere) swimming straight ahead. S. robledoensis consists of repeated pes imprints separated by discontinuous, L-shaped imprints (body traces). It is interpreted as a trackway of an 'amphibian' swimming in a similar manner to the motion of a side-winding snake. The producer of S. robledoensis is more distinctive than in B. delicatulus , and is suggestive of the lysorophian Brachydectes . This is the first locomotory trace to be assigned to this 'amphibian' group. 相似文献
18.
Abstract: The holotype and only known specimen of Geikia locusticeps (von Huene, 1942) from the Kawinga Formation (Tatarian) of Kingori, south-west Tanzania, is redescribed. It is compared to the type specimen of the Tanzanian geikiid Pelanomodon tuberosus von Huene, 1942. It is demonstrated that G. locusticeps is a juvenile specimen of P. tuberosus . Ontogenetic changes in the skull of this taxon are recorded. They mainly concern the degree of skull ornamentation, whereas the major osteological and proportional features remain remarkably constant. Pelanomodon tuberosus is referred to Geikia locusticeps as a junior subjective synonym. G. locusticeps is compared to Geikia elginensis and South African representatives of Pelanomodon . G. locusticeps is demonstrated to represent a valid species, one that is so far endemic to the Ruhuhu Basin of south-west Tanzania. The relevance of the orientation of the postorbital bone to Permian pristerodontian systematics is discussed, and a phylogenetic analysis and new diagnosis for the family Geikiidae are presented. 相似文献
19.
Michael W. Maisch 《Palaeontology》2002,45(2):343-359
A new genus and species of late Permian dicynodont, Kwazulusaurus shakai , is described on the basis of a complete skull from the late Permian Dicynodon Assemblage Zone of the South African Beaufort Group. It is an advanced form which shows characters, such as the shape of the snout and the loss of the ectopterygoid, that link it to the early Triassic genus Lystrosaurus. Kwazulusaurus represents the most basal member of the lystrosaurian lineage. The phylogeny of progressive pristerodontian dicynodonts is discussed. It appears possible that the Kannemeyeriiformes and Lystrosauridae do not form a monophylum, as previously assumed. Instead a sister-group relationship between lystrosaurids and dicynodontids plus kannemeyeriiforms is suggested. 相似文献
20.
New Grylloblattids of the family Megakhosaridae (Insecta: Grylloblattida) from the Permian of Russia
D. S. Aristov 《Paleontological Journal》2008,42(3):269-272
New Megakhosaridae (Insecta: Grylloblattida) are described from the Permian of Russia: Ivakhosara pectinimedia gen. et sp. nov., Megakhosarina intricata sp. nov. and M. minuscula sp. nov. from the Lower Kazanian of Soyana (Arkhangelsk Region), M. magna sp. nov. from the Urzhumian of Chepanikha (Udmurtia), Kargalokhosara terraefossa gen. et sp. nov. from the Urzhumian of Kargala (Orenburg Region), and Alekhosara reticulata gen. et sp. nov. from the Severodvinian of Novo-Aleksandrovka (Orenburg Region). 相似文献