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1.
Abstract: The first abundant, well‐preserved fossils of the unusual archosauromorph reptile Trilophosaurus jacobsi Murry are from an Upper Triassic bonebed in the lowermost Trujillo Formation of the Chinle Group in Borden County, Texas. A nearly complete left side of the skull and incomplete but articulated mandible of a juvenile individual demonstrate that Trilophosaurus jacobsi Murry is referable to Trilophosaurus, so the putative procolophonid genus Chinleogomphius is a junior objective synonym of Trilophosaurus. Features of T. jacobsi that diagnose it from T. buettneri include asymmetrical, tricuspate teeth in which the central cusp is taller than the marginal cusp, polygonal in cross‐section and displaced slightly lingually; the lingual cusp is low, transversely broadened and anteroposteriorly compressed; teeth with prominent cingula along the mesial and distal margins; and paired sagittal (parasagittal) crests composed of portions of the postfrontals and the parietals, as well as a relatively broad skull roof between the supratemporal fenestrae. We also re‐illustrate and re‐describe the holotypes of both Trilophosaurus buettneri Case and T. jacobsi Murry. T. jacobsi is primarily Adamanian in age, and the lowest occurrence of T. jacobsi is stratigraphically above that of T. buettneri. Therefore, T. buettneri is an Otischalkian–Adamanian index taxon, and T. jacobsi is an Adamanian–?earliest Revueltian index taxon. Trilophosaurus teeth are readily identifiable to species and therefore identifiable as isolated fossils.  相似文献   

2.
We describe an early juvenile specimen (ZMNH M8812) of Bolong yixianensis from the Yixian Formation (Lower Cretaceous) of Ningcheng County, Nei Mongol, China. The specimen consists of an almost complete skeleton preserved two-dimensionally on a slab. The short and deep skull proportions and unfused neurocentral sutures in most preserved vertebrae suggest that the ZMNH M8812 is a juvenile individual. Osteohistological study confirms a very early developmental stage. The study reveals the ontogenetic changes of Bolong for the first time. The specimen revealed one additional autapomorphy for Bolong yixianensis: the lingual face of the maxillary crown is bounded by thickened mesial and distal margins and bisected by a prominent median principal ridge. The study revealed the following ontogenetic trends of Bolong: increased tooth rows in both maxilla and dentary, increased robustness of the jugal and scapula, the radius and ulna become more robust and shorter relative to the hindlimb and the metatarsals become proportionally shorter. ZMNH M8812 represents the first juvenile non-hadrosaurid iguanodontian specimen described from the Lower Cretaceous of eastern Asia.  相似文献   

3.
GERALD MAYR 《Palaeontology》2008,51(5):1107-1116
Abstract: The first substantial skull of a very large Paleogene bony‐toothed bird (Pelagornithidae) is described from the Lower Eocene London Clay of the Isle of Sheppey in England. The specimen is assigned to Dasornis emuinus (Bowerbank), based on a taxonomic revision of the large London Clay Pelagornithidae. Very large bony‐toothed birds from the London Clay were known previously from fragmentary remains of non‐comparable skeletal elements only, and Dasornis londinensis Owen, Argillornis emuinus (Bowerbank), A. longipennis Owen, and Neptuniavis miranda Harrison and Walker are considered junior synonyms of D. emuinus. The new specimen allows a definitive assignment of Dasornis to the Pelagornithidae and documents that this taxon closely resembles other bony‐toothed birds in cranial morphology. It is hypothesized that giant size (i.e. a wingspan above 4 m) evolved only once within Pelagornithidae and that Dasornis emuinus is the sister taxon of the giant Neogene bony‐toothed birds, which share a derived wing morphology.  相似文献   

4.
Abstract: Peloneustes philarchus is the most abundant pliosaurid from the Peterborough Member of the Oxford Clay Formation (Callovian) of the UK. It is a valid taxon possessing a unique character combination, including a single autapomorphy: the interdentary symphysis is raised dorsally on a narrow platform. Twenty‐one specimens can be positively referred to P. philarchus. However, other specimens previously referred to Peloneustes, from the Peterborough Member near Peterborough, and the lower Oxfordian strata of Marquise, northern France, represent distinct, unnamed taxa. The skull of P. philarchus is described in detail, including new information from an uncrushed, three‐dimensionally preserved specimen and a specimen with a well‐preserved palate. Well‐preserved material clearly indicates that P. philarchus lacked nasals, but possessed a lacrimal. A previously unrecognised ‘palpebral’ forms part of the dorsal orbit margin adjacent to the prefrontal. The number of maxillary (30–31) and dentary (36–44) alveoli, the number of dentary alveoli adjacent to the mandibular symphysis (13–15), the number of foramina on the frontal and jugal, the breadth of the parasphenoid, breadth of the anterior (narial) process of the palatine and the presence of a lappet of the angular that extends onto the posterodorsal surface of the retroarticular process vary among individuals but are not considered sufficient to justify the recognition of new taxa. The presence of an open palpebral–prefrontal suture, the size of the ventral midline tubercle of the basioccipital and the presence of an anterior interpterygoid vacuity seem to vary with body size.  相似文献   

5.
A sciadopityaceous seed cone, Sciadopityostrobus kerae, gen. et sp. nov., is described on the basis of a permineralized specimen from the Upper Cretaceous (Cenomanian–Coniacian) of Hokkaido, Japan. The peel method was applied for anatomical observations. The seed cone consists of a cone axis receiving numerous cone scale complexes that are arranged helically. Each complex generally has five inverted ovules that are oriented adaxially. The cone is similar to those of living Sciadopitys verticillata with respect to its peltate cone scale complex, with free apices of both bract and ovuliferous scale, trichomes on the bract, and a trifurcated ovuliferous scale strand. In the fossil, the bract and ovuliferous scale strands fuse with each other in the basal part of the cone scale complex, while S. verticillata bract and ovuliferous scale strands are derived separately from the vascular cylinder and remain separate throughout their length. The present specimen is one of the oldest records of structurally preserved cones that can be assigned to the family Sciadopityaceae.  相似文献   

6.
A new species of Trigonocarpus Brongniart is described from the level of the Herrin (No. 6) Coal (Carbondale Formation, Kewanee Group) at Carterville, Illinois. The seed is three dimensionally preserved by authigenic cementation and exhibits a well preserved nucellar cast, integument and micropylar region. The specimen represents the largest pteridosperm compression-impression seed collected in North America and measures 10 cm from the apex of the micropyle to the chalazal end, and at least 5 cm in breadth. Trigonocarpus leeanus sp. n. is compared to the remaining forty-three taxa within the genus, and specifically with Trigonocarpus grandis Lesquereux, the one species with dimensions approaching it. An emended diagnosis, with designation of a lectotype, is presented for Trigonocarpus grandis. Correlation of the features displayed by Trigonocarpus leeanus sp. n. and the petrified taxa within Pachytesta Brongniart is attempted.  相似文献   

7.
记述了产自内蒙古呼和勃尔和剖面阿山头组的始施氏貘(Schlosseria magister)幼年头骨、头骨碎片及产自额尔登敖包底白层的S.magister成年头骨。幼年头骨在脊齿貘科属首次描述,成年头骨材料也是目前S.magister中首次描述。幼年头骨主要特征如下:头骨细长,脑颅部略有扩张,有眶后突,眶后收缩明显,矢状脊轻微发育;鼻切迹浅,位于前臼齿列之前,由前颌骨和鼻骨构成;眼眶大,眶前缘位于M1后部上方,眶下孔位于DP3-4之上;基蝶骨向后向中央逐渐加厚,末端隆起;翼蝶骨很大,从腹面看向后向背侧扩展,末端形成三角形的翼蝶骨突,覆盖在卵圆孔上;岩骨岬部表面有内颈动脉及其分支留下的3条沟痕;最内侧的为内颈动脉内侧沟,沿着岬部弯曲前行至最前部;镫骨动脉沟短小,横跨在圆窗前腹侧;岬动脉沟最长,起始于卵圆窗前内侧,沿岬部向前延伸;弓形下窝所在位置平滑,无凹陷。S.magister乳颊齿主要特征如下:DP2冠面大致呈三角形,前窄后宽,前缘较尖,长明显大于宽;外脊上仅有一个中央主尖前尖,一个非常不明显的小棱(可能为雏形的原脊)紧贴在前尖后舌侧壁上;前、后附尖不明显。DP3冠面呈梯形,与DP2相比明显增大,亚臼齿化,前附尖和后附尖略大,原、后脊明显。前尖大,后尖尚未分离;原尖很弱,几乎无法辨认,原脊低且不发育;次尖大而钝,比原尖更靠舌侧,后脊比原脊略发育,中部具小的后小尖;后脊在次尖处拐向后唇侧,使得磨蚀面呈V形。DP4冠面近方形,完全臼齿化,后尖已从外脊上分化出来,比前尖稍小,向舌侧倾斜,后尖肋明显;舌侧尖、脊发育完好,原尖和次尖大而钝,原脊、后脊近乎平行,比DP3的更高更长;两条脊分别在原尖和后尖处拐向后唇侧方,形成V形的磨蚀面。S.magister在由幼年向成年转变的过程中,主要变化趋势如下:1)吻部特征不同,主要表现为鼻切迹的位置、形态以及与之相关的前颌骨、上颌骨形态的差异。幼年头骨的鼻切迹位于前臼齿列之前,由前颌骨和鼻骨组成;成年头骨的鼻切迹后缩至M1-2之上,由鼻骨和上颌骨组成,并且因鼻切迹后缩造成鼻骨不与前颌骨接触。幼年和成年个体上颌骨的整体形态,眶前窝、眶下孔的位置和形态都差异显著。2)与咀嚼功能相关的结构改变。幼年个体的矢状脊微弱,而成年个体的则高且突起,暗示了后者具有相对强大的颞肌,以适应咀嚼功能。对比发现,S.magister与Lophialetes expeditus成年头骨在大小、整体形态和一些具有分类意义的特征上(如鼻骨和泪骨、前颌骨的接触方式,眶后突、关节后突、下颌关节窝的形状,矢状脊的高度等)非常接近。参照童永生、雷奕振(1984)对脊齿貘类头骨的划分方法,将Schlosseria magister的头骨与L.expeditus的划为一组,同时纠正了原有划分方案中存在的问题。  相似文献   

8.
Abstract: A new genus and species of basal non‐Viverravidae Carnivoramorpha, Dawsonicyon isami, is named and described. This new taxon is based upon DMNH 19585, an almost complete skeleton, which was collected from the Black’s Fork Member (informal ‘Bridger B’ subunit) of the Bridger Formation in southwestern Wyoming, USA. The specimen is incorporated into an existing craniodental data matrix, and the associated phylogenetic analyses support the identification of this species as a new basal carnivoramorphan. This new taxon is dentally compared to all known genera of non‐viverravid basal carnivoramorphans, as well as with all known species of the problematic genus Miacis. Postcrania are compared in detail with other described specimens of non‐viverravid basal carnivoramorphans and more generally with known postcrania of viverravids. Preliminary functional interpretations of a scansorial locomotor mode are offered for this new taxon. Its implications for the diversity of middle Eocene basal carnivoramorphans is briefly discussed, including expansion of the already high diversity in the Black’s Fork Member of the Bridger Formation (at least 11 species in 8 genera).  相似文献   

9.
Abstract: Recent revision of the marine metriorhynchid crocodilians indicates that a partial skull previously assigned to the species Metriorhynchus superciliosus and newly discovered postcranial elements from the Kimmeridge Clay of Westbury, Wiltshire belong to a new species of metriorhynchid. This material is herein described and referred to a new species of the genus Dakosaurus, characterised by four apomorphies: the size and shape of the enlarged supratemporal fossae; relatively large teeth, and half the number in relatives; the robust and unornamented cranium; and the angle that the prefrontal makes with the long axis of the skull. In a new phylogenetic analysis, Dakosaurus carpenteri sp. nov. is the basal member of a clade containing also D. maximus and D. andiniensis: it is not so short‐snouted and its teeth are not so few and large as in the other two species, but the new form illustrates the ecological transition among metriorhynchids from a piscivorous diet to high‐order carnivory.  相似文献   

10.
Abstract: A portion of pterosaur skull from the Romualdo Member of the Santana Formation (?Albian–?Turonian, Cretaceous) of north‐east Brazil provides new data on the morphology and ontogeny of azhdarchoid pterosaur cranial crests. The specimen consists of parts of the cranial bones posterodorsal to the nasoantorbital fenestra, including partial nasals, lacrimals, frontals and possibly the parietals. A posterodorsally directed premaxillary crest with a concave posterior border is located dorsal to the posterior border of the nasoantorbital fenestra. A well‐defined suture indicates overlapping, posterodorsally directed growth of the premaxilla over the skull roof, suggesting that the generation of the premaxillary crest is a late ontogenetic feature and thus probably related to sexual display. The systematics of Tupuxuara and its relationship to other azhdarchoids is reviewed and a cladistic analysis of the group is presented. Tupuxuara is found to be the sister‐taxon to Azhdarchidae. Tupuxuara longicristatus Kellner and Campos, 1988 is argued to be the only valid named species in this genus and Thalassodromeus Kellner and Campos, 2002 is considered a junior subjective synonym of this taxon. As originally conceived, Tapejaridae is paraphyletic: a new, more restrictive version of Tapejaridae (including Tapejara and Sinopterus dongi) might exist, but its monophyly is weakly supported. Furthermore, Tapejara was found to be paraphyletic in all trees.  相似文献   

11.
12.
Abstract: A new spinicaudatan genus and species, Ethmosestheria mahajangaensis gen. et sp. nov., is described from the Anembalemba Member (Upper Cretaceous, Maastrichtian) of the Maevarano Formation, Mahajanga Basin, Madagascar. This is the first spinicaudatan reported from the post‐Triassic Mesozoic of Madagascar. The new species is assigned to the family Antronestheriidae based on the cavernous or sievelike ornamentation on the carapace. Of well‐documented Mesozoic spinicaudatan genera, Ethmosestheria mahajangaensis is most closely related to Antronestheria Chen and Hudson from the Great Estuarine Group (Jurassic) of Scotland. However, relatively poor documentation of the ornamentation of most Gondwanan Mesozoic spinicaudatan species precludes detailed comparison among taxa. Ethmosestheria mahajangaensis exhibits ontogenetic trends in carapace growth: a change in carapace outline from subcircular/subelliptical to elliptical, and from very wide juvenile growth bands to narrow adult growth bands. Ornamentation style, however, does not vary with ontogeny. Ethmosestheria mahajangaensis individuals lived in temporary pools in a broad channel‐belt system within a semiarid environment; preserved desiccation structures on carapaces indicate seasonal drying out of pools within the river system. Specimens of Ethmosestheria mahajangaensis are preserved with exquisite detail in debris flow deposits; these are the first spinicaudatans reported from debris flow deposits. These deposits also contain a varied vertebrate fauna, including dinosaurs, crocodyliforms, turtles, and frogs. Rapid entombment of the spinicaudatan carapaces likely promoted early fossil diagenesis leading to highly detailed preservation.  相似文献   

13.
Abstract: Palaeoctopus pelagicus sp. nov. is described from the early Turonian Vallecillo Limestone in north‐eastern Mexico. The species represents the first record of a fossil octopod from the Americas and the second species of the genus Palaeoctopus. The holotype and only known specimen preserves one half of an originally bipartite gladius vestige. Soft parts are not preserved. The gladius vestige is distinguished from P. newboldi from the Santonian Limestone of Lebanon by the arrangement of fields, striation and reinforcements. The new material supports previous ideas suggesting that the paired stylets of modern Octopoda evolved through gradual reduction of a Teudopsis‐like gladius via a transitional stage similar to Palaeoctopus. The origin of Octopoda and Cirroctopoda likely dates back to a period between the Toarcian (180 Ma) and the early Turonian (93 Ma). Palaeoecological conditions in the Vallecillo ocean suggest that P. pelagicus sp. nov. inhabited the pelagic shelf. Hostile low oxygen conditions on the sea floor exclude a benthic mode of life for P. pelagicus sp. nov.  相似文献   

14.
The Middle Jurassic was a critical time in the evolution of theropod dinosaurs, highlighted by the origination and initial radiation of the large‐bodied and morphologically diverse Tetanurae. Middle Jurassic tetanurans are rare, but have been described from Europe, South America and China. In particular, China has yielded a number of potential basal tetanurans, but these have received little detailed treatment in the literature. Chief among these is Monolophosaurus jiangi, known from a single skeleton that includes a nearly complete and well‐preserved skull characterized by a bizarre cranial crest. Here, we redescribe the skull of Monolophosaurus, which is one of the most complete basal tetanuran skulls known and the only quality source of cranial data for Middle Jurassic Chinese theropods. The cranial crest is atomized into a number of autapomorphic features and several characters confirm the tetanuran affinities of Monolophosaurus. However, several features suggest a basal position within Tetanurae, which contrasts with most published cladistic analyses, which place Monolophosaurus within the more derived Allosauroidea. Cranial characters previously used to diagnose Allosauroidea are reviewed and most are found to have a much wider distribution among Theropoda, eroding an allosauroid position for Monolophosaurus and questioning allosauroid monophyly. The use of phylogenetic characters relating to theropod cranial crests is discussed and a protocol for future use is given. The systematic position of Guanlong wucaii is reviewed, and a basal tyrannosauroid affinity is upheld contrary to one suggestion of a close relationship between this taxon and Monolophosaurus. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 573–607.  相似文献   

15.
A new metriorhynchid crocodylomorph from the Lower Kimmeridge Clay Formation (Kimmeridgian, Upper Jurassic) of England is described. This specimen, a three‐dimensionally preserved skull and left mandibular ramus, is referred to a new species: T orvoneustes coryphaeus sp. nov. Within the genus Torvoneustes, T . coryphaeus sp. nov. is unique as it has a long anteromedial process of the frontal, ornamented dermatocranium, and the supraorbital notch forms a strongly acute angle. Our phylogenetic analysis confirms the placement of this specimen in Torvoneustes. The dentition of T . coryphaeus sp. nov. , like that of the type species, has a blunt apex, crown basal–mid regions with numerous tightly packed apicobasally aligned ridges, and apical region with an anastomosed pattern of ridges that interact with the carinae. Within Thalattosuchia these dental characteristics are only found in Torvoneustes and the teleosaurid Machimosaurus. The heavily ornamented dermatocranium of T . coryphaeus sp. nov. is in contrast to the unornamented (nasals and frontal)–lightly ornamented (maxillae and premaxillae) pattern seen in Torvoneustes carpenteri. Curiously, this pattern of reduction and loss of dermatocranium ornamentation is also observed in Metriorhynchus, Dakosaurus, and the subclade Rhacheosaurini. We hypothesize that the ‘smooth’ dermatocranium of Late Jurassic metriorhynchids evolved independently in each subclade (parallel evolution), and would have reduced drag, thereby making locomotion through water more energy efficient. © 2013 The Linnean Society of London  相似文献   

16.
根据发现于辽宁西部建昌早白垩世九佛堂组一件保存较为完好的标本,描述了原始今鸟类一新属种,李氏叉尾鸟(Schizooura lii gen.et sp.nov.)。系统发育分析表明,它较建昌鸟和古喙鸟进步,但又较热河生物群中其他已知的今鸟类原始。这一新种叉骨呈Ⅴ型,且具有一短的叉骨突,这是这一特征首次在早白垩世今鸟中发现。其胸骨加长,后缘无窗孔,且无很深的凹口。肱骨三角肌脊膨大,近乎达到肱骨长的一半。新鸟的头骨保存较好,显示其具喙的特征,前颌骨直接与额骨相关节。值得关注的是,这件标本首次展示了在中生代鸟类中,除扇形尾羽之外的第二种尾羽类型。新标本具叉形尾羽,中间分隔明显。对现生鸟类的研究表明,叉尾型的空气动力学效率比扇尾型要低,但在性选择方面具有优势。这一新的发现说明,在热河生物群生活的森林环境中,今鸟类的基干种类在尾羽性状上或许已经存在着不同的选择策略。  相似文献   

17.
18.
The genus Probactrosaurus was first established for material discovered by a joint Russian/Chinese expedition to the Chinese autonomous region of Neimongol (Inner Mongolia). Fossils were collected at a site named Maorty (= Maortu). Material attributable to ornithopod dinosaurs was considered sufficiently distinct to permit the definition of two species of the new genus: Probactrosaurus gobiensis and P. alashanicus. The former species was based on a considerable quantity of skeletal material, much of which is still to be found in the collections of the Palaeontological Institute (PIN), Moscow. The latter was based on far less well‐preserved specimens, including a holotype (a posterior skull roof) that can no longer be found in the collections of the PIN and which, along with other materials, was reportedly returned to the Institute of Vertebrate Palaeontology and Palaeoanthropology, Beijing. Some remnants of the original material attributed to P. alashanicus have been located in the PIN collections. Both taxa, established by A. K. Rozhdestvensky, are re‐described using all of the available material collected during the early Sino‐Soviet expeditions. Probactrosaurus alashanicus is considered to be a junior subjective synonym of P. gobiensis. Further comparisons are made with the recently described species Probactrosaurus mazongshanensis Lu, 1997. The latter does not appear to be referable to the genus Probactrosaurus. Probactrosaurus is a gracile ornithopod (ranging between 4 and 6 m in length). The skull is unadorned by any form of cranial crest; however, the premaxillary beak is deflected ventrally and the dentition is similar to that seen in more derived hadrosaurid ornithopods. The postcranial skeleton is notable for its gracility, in particular the elongate forearm and manus, and the retention of a small, conical pollex spine. Systematic analysis suggests that P. gobiensis is a derived non‐hadrosaurid iguanodontian ornithopod and the basal sister‐taxon to the clade Hadrosauridae. The phylogeny of currently known iguanodontians is reviewed. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136 , 113–144.  相似文献   

19.
Abstract: A new fossil osteoglossid fish, Taverneichthys bikanericus gen. et sp. nov. and an unnamed but probable new species of ?Lepisosteus (Lepisosteidae) are described from the subsurface beds of the Palana (lignite) Formation near Bikaner, western Rajasthan, India. T. bikanericus is founded on a skull, which is the first osteoglossid skull from the Indian subcontinent, whereas ?Lepisosteus sp. is represented by a part of its trunk covered with ganoid scales. The taxonomic assignment of the latter specimen to gars is based on the micro‐ and ultrastructure of its scales. Taverneichthys is included in the Osteoglossinae because it shares at least three of the seven diagnostic characters of the subfamily: (1) jaw articulation behind the vertical midline of orbit, (2) palatine and ectopterygoid fused to form palato‐ectopterygoid, and (3) horizontal arm of preopercle short, ending anteriorly behind orbit (inferred). It is characterized by a considerably larger dermethmoid bone and the two nasals that are in contact with each other behind it separating this bone from the frontals. In this respect it is more evolved than Cretophareodus and Phareodus, and closer to Brychaetus, Musperia, Opsithrissops and modern osteoglossids. The fossils documented herein are the first vertebrate remains from the Palana Formation. They were recovered from a highly indurated greyish‐black calcareous shale approximately 90 m below ground level from a dug‐well section. The occurrence of fossil remains of osteoglossid and lepisosteid fish in the Palana Formation, both of which are among the major predators of a terrestrial aquatic community, and their association with the crocodilian remains, are indicative of the mature and diverse nature of the Palana vertebrate community. It postulates the recovery of a varied assemblage of vertebrates, especially fish and crocodilians and possibly also mammals. The association of osteoglossid and lepisosteid fish characterizes a dominantly freshwater deposit and is consistent with a Paleocene age for the Palana Formation. The known distribution of fossil and living osteoglossid and lepisosteid fish suggests a marked shift in their climatic adaptability in time and space. Their close association in the fossil record, especially in the Indian subcontinent, is well documented, but today they thrive in different climatic zones.  相似文献   

20.
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