Do extraordinarily high growth rates in Permo‐Triassic dicynodonts (Therapsida,Anomodontia) explain their success before and after the end‐Permian extinction?

Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo‐Triassic. They include Lystrosaurus, one of the few taxa known to survive the end‐Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end‐Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end‐Permian extinction and its dominance during the postextinction recovery period. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 341–365.     

Terrestrial tetrapods and the end Permian event: A comparison of analyses

Previous analyses of changes in diversity of Permo‐Triassic tetrapods are reviewed and compared. Biases inherent in such studies which distort the picture of diversity change are discussed. A new analysis of change in generic diversity of the tetrapods of the Karoo Basin, South Africa is presented. Various factors which could bias the results, namely, inconsistent taxonomy, insensitive stratigraphy, area of exposure per time interval, and differing intensity of collecting are addressed and corrections made for them. The results of the new analysis are compared to those of previous ones. In particular it is noted that, contrary to the results of other studies, large decreases in generic number are recorded not once, but twice in the Late Permian sediments, the second occurring in sediments dating from well before the close of that Period. It is concluded that stratigraphic sensitivity is the most important biasing factor in the present analysis and the implications of this for other diversity studies, and for explanations of diversity change, are emphasized.     

When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin,South Africa

A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian–Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74–80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U–Pb zircon date (CA-TIMS method) of 260.259 ± 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions.     

Late Carboniferous palynostratigraphy of the Itararé Subgroup, northeastern Paraná Basin, Brazil

A new biozonation is proposed for the Late Carboniferous strata of the northeastern Paraná Basin (São Paulo and Paraná States), based on well-preserved palynological assemblages recovered from outcrops and core samples retrieved from the Itararé Subgroup. Assemblages include forty-nine species of trilete spores and twenty-five pollen species. The oldest biozone, the Ahrensisporites cristatus Interval Zone (AcZ), in the basal portion of the Itararé Subgroup, includes eleven exclusive spore species, and is assigned a Pennsylvanian (late Bashkirian to Kasimovian) age. The overlying proposed biozone, the Crucisaccites monoletus Interval Zone (CmZ), dated late Pennsylvanian (Kasimovian to Gzhelian), ranges approximately from the top of the lower portion to the middle portion of the Itararé Subgroup, bears only one exclusive species of pollen. Both zones are characterized by the dominance of trilete spores and monosaccate pollen grains, including also few taeniate pollen grains. Furthermore, the basal Protohaploxypinus goraiensis Subzone of the Vittatina costabilis Interval Zone (VcZ) is broadly recognized for the first time in the upper portion of the Itararé Subgroup in the northeastern Paraná Basin. This subzone is attributed to the Early Permian (Early Cisuralian), and is characterized by the dominance of monosaccate pollen grains, a significant increase of taeniate grains (mainly Protohaploxypinus spp.), apart from the appearance of polyplicate pollen (Vittatina spp.). Reference sections and the main characteristics of the two new zones (AcZ and CmZ) are presented, along with a preliminary palynological correlation and discussion on their ages.     

我国北方石炭-二叠系牙形刺序列再认识

文中根据当前比较统一的牙形刺分带原则,对我国北方石炭二叠系的牙形刺序列进行了研究和重新定义。我国北方地区石炭二叠系的牙形刺带或组合带由上而下可综合如下：Sweetognathus whitei,S.inornatus,Streptognathodus barskovi,S.isolatus,S.elegantulus-S.oppletus,Idiognathodus magnificus-Neognathodus roundyi,Idiognathodus delicatus-Neognathodus bothrops,Idiognathoides corrugatus-I.sinuatus,Declinognathodus noduliferus,Gnathodus bilineatus bollandensis和Gnathodus bilineatus bilineatus带或组合带。本文同时介绍了牙形刺带和组合带在我国北方的分布、时代及其对比。     

A primitive anomodont therapsid from the base of the Beaufort Group (Upper Permian) of South Africa

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.     

The Upper Permian articulate Phyllotheca australis from South Africa

RAYNER, R. J., 1992. The Upper Permian articulate Phyllotheca australis from South Africa. The taxonomic position of two fossil articulates, which form an important element of the Permian Gondwana flora, is examined in the light of recent collections from South Africa. Vegetative and fertile axes, dispersed and attached sporangia, in-situ spores, isolated and attached whorls of leaves, rhizomes bearing roots and branches, naked axes and a permineralized axis are all assigned to Phyllotheca australis. The large numbers of axes with attached sporangia allow a reinterpretation of the fertile structure and the specific diagnosis is emended. Although it is recognized that the fossils assigned to this taxon may represent a species complex, there exist no clear morphological discontinuities between the material previously assigned to P. australis and P. indica from widely separated Gondwanan localities. Phyllotheca australis was common throughout Gondwana, and is a reliable index fossil of the Upper Permian.     

Morphologic variation of two key biostratigraphical proteaceous-like pollen taxa across the Cretaceous–Paleogene boundary in northern South America

Echitriporites trianguliformis and E. suescae comb. nov. are two species of proteaceous-like triaperturate pollen that have been widely reported in several sedimentary sequences from northern South America, especially in Colombia and Venezuela. Despite their biostratigraphic significance and because of their morphological similarity, distinction between the two species has been difficult, leading to a biased understanding of their chronostratigraphic ranges. In this study, we compare 75 pollen grains spanning the Maastrichtian–Danian time interval through traditional and geometric morphometrics, and a newly proposed Procrustes-based method (index of pollen curvature). Traditional assessments show subtle variation between specimens; however, geometric morphometrics and the curvature index allow quantifying morphological differences in the degree of concavity-convexity through time. Therefore, geometric morphometrics and curvature index results enable us to constrain the stratigraphic ranges of both taxa. We suggest a coetaneous range for E. trianguliformis and E. suescae comb. nov. during the Late Cretaceous, but the presence of only E. trianguliformis after the Cretaceous–Paleogene boundary event. In addition, we propose a threshold value of 1.5 µm for the curvature index as a tool for distinguishing between these two taxa. We conclude that the combination of geometric morphometrics and the curvature index provides a powerful tool to distinguish between morphological closely-related pollen taxa that are difficult to distinguish through both light microscope visual comparisons and statistical analysis of morphometric measurements.     

新疆乌伦古河流域第三纪哺乳动物地层研究的新成果

新疆准噶尔盆地北缘中、新生代地层广泛出露,２０世纪５０年代,对这一地区的中、新生代地层的系统研究工作业已开展。地质部６３１地质队在该地区进行大面积地质填图,新疆石油管理局开展了有关地质问题的综合性专题研究。１９８２年和１９８３年中国科学院古脊椎动物与古人类研究所在新疆石油管理局的支持下,组队前往该区进行中、新生代生物地层研究工作,并于８０年代末与９０年代初提交了一批生物地层和古哺乳动物研究文章,进一步提高了该地区第三纪地层的研究程度。由于工作区地处中亚,位于青藏高原以北,西面邻近古土尔盖海峡,东…     

Osteomyelitis in a 265-million-year-old titanosuchid (Dinocephalia,Therapsida)

Abstract

Analytical 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.     

镇江地区上二叠统—下三叠统的牙形刺

详细描述了采自镇江附近１１－１,１１－２,７９－８号等钻孔的上二叠统—下三叠统的牙形刺化石共１１属２８种,建立了６个牙形刺化石带,其中上二叠统１个、下三叠统５个,并以牙形刺带为基础,进行了国内外对比。     

Novel double wing morphology revealed in a South African ovuliferous glossopterid fructification: Bifariala intermittens (Plumstead 1958) comb. nov.

Plumstead (1958) established Hirsutum intermittens for glossopterid fructifications with a putative bi-sporangiate, bi-valved architecture but later workers reinterpreted the fossils predominantly as ovuliferous, dorsiventrally flattened, bilaterally symmetrical organs, with a central seed-bearing receptacle and a single finely striate peripheral wing. The wing morphology is central to both the generic and specific diagnoses. New analysis of many South African impressions reveals the presence of two superposed wings flanking the flattened receptacle of H. intermittens. One wing is radially fluted and striated with rounded basal lobes, whereas the other has distinctive distally arched striations and an extended apex. The double-winged structure is unlike that of other glossopterid fertile organs and probably accounts for Plumstead's misinterpretation of the fructification as bivalvate. The specimens are assigned to Bifariala intermittens (Plumstead, 1958) comb. nov., emend. Prevec because Hirsutum is unacceptable according to ICBN rules. Revelation of novel architectural details highlights the value of impression fossils for resolving the gross structure of gymnosperm fertile organs. The newly defined second wing provides an additional character to be considered in the search for homologies of the ovule outer integument or cupules in derived seed-plants.     

新疆准噶尔盆地北缘第三纪地层古生物研究新进展

近两年对准噶尔盆地北缘第三纪地层进行了进一步调查和研究,在索索泉组和哈拉玛盖组内发现了新的化石层位。对新发现的哺乳动物的研究表明在勒布勒津地区索索泉组顶部的沉积物时代为中中新世,下部的沉积物时代不晚于晚渐新世,中新世与渐新世地层的界线应在索索泉组内寻找。新发现的动物群分子Cricetodonsp．nov．和Tachyoryctoidessp．nov.指示哈拉玛盖动物群的时代应重新考虑,有可能早于丁家二沟动物群。     

Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa

Lystrosaurus is one of the few therapsid genera that survived the end-Permian mass extinction, and the only genus to have done so in abundance. This study identifies which species of Lystrosaurus have been recovered from Permian and Triassic strata to determine changes in the species composition across the Permo–Triassic (P–T) boundary in the Karoo Basin of South Africa. Data generated from museum collections and recent fieldwork were used to stratigraphically arrange a total of 189 Lystrosaurus specimens to determine which species survived the extinction event. Results reveal that L. curvatus and L. maccaigi lived together on the Karoo floodplains immediately before the extinction event. L. maccaigi did not survive into the Triassic in South Africa. L. curvatus survived, but did not flourish and soon became extinct. Two new species of Lystrosaurus , L. murrayi and L. declivis , appeared in the Early Triassic. It is possible that L. murrayi and L. declivis occupied different niches to L. maccaigi and L. curvatus , and had special adaptations that were advantageous in an Early Triassic environment. We suggest that L. maccaigi may be used as a biostratigraphic marker to indicate latest Permian strata in South Africa and that, in support of previous proposals, the genus Lystrosaurus should not be used as a sole indicator of Triassic-aged strata. Our field data also show that L. curvatus may be regarded as a biostratigraphic indicator of the P–T boundary interval.