Stephanie E. Pierce2014-05-06 3:34 PM

英国萨默塞特早侏罗纪(托阿尔,下侏罗统)佩拉古鳄型族,1841(中真鳄类:海鳄亚目) Pelagosaurus typus Bronn, 1841 (Mesoeucrocodylia: Thalattosuchia) from the Upper Lias (Toarcian, Lower Jurassic) of Somerset, England

Abstact

The thalattosuchian crocodyliform Pelagosaurus typus Bronn, 1841 is fully documented and described from the Upper Lias (Toarcian, Lower Jurassic) of England. The material under study is part of a historical collection made by Charles Moore (1814–1881) at Strawberry Bank (Ilminster, Somerset, England) around 1848. Apomomorphic features of the genus include: sculpturing on almost the entire skull and mandible with extensive sculpturing on the prefrontal, lachrymal, frontal, parietal, temporal arcade and the posterior extent of the mandible; 30 piercing teeth on each side of the upper and lower jaws; small, shallow, egg-shaped antorbital fenestra present within the lachrymal and maxilla; supratemporal fenestrae short anteroposteriorly; paired frontal; anterior margin of internal choana tapers anteriorly between the paired palatines; and presence of a choanal septum on the palatine and pterygoid. Pelagosaurus was a small, exceedingly long-snouted, gracile crocodyliform whose diet probably consisted of small fishes, crustaceans and possibly insects. The small-bodied fish Leptolepis is confirmed as part of its diet as a specimen is found in the rib cage of a small juvenile Pelagosaurus. Laterally placed eyes suggest that this species actively pursued its prey rather than sitting and waiting at the water surface. The phylogenetic position of Pelagosaurus has been debated. Pelagosaurus possesses the majority of teleosaurid apomorphies, including: four premaxillary teeth; small prefrontal; lachrymal visible in dorsal aspect; presence of mandibular fenestrae; dermal armor; and a straight tail; however, these are all plesiomorphic for the Crocodyliformes in general. There also appear to be problems when defining the proposed metriorhynchid features of Pelagosaurus (i.e., broad nasal, large frontal, lateral orbit, sclerotic ring and arrangement of prefrontal-lachrymal). Moreover, characters that have been used in past cladistic analyses are either incorrect or too simplistic. Accordingly, Pelagosaurus is considered to belong to the Thalattosuchia incertae sedis until a more thorough phylogenetic investigation is conducted.

KEYWORDS

SHARE & LIKE

COMMENTS

ABOUT THE AUTHOR

Stephanie E. Pierce

0 Following 0 Fans 0 Projects 19 Articles

SIMILAR ARTICLES

AbstractAlthough continuing professional development (CPD) is regarded as mandatory by the Royal College of Veterinary Surgeons, it is not yet a statut

Read More

论文摘要脊柱结构已被用作定义和诊断早期四足动物类群的关键性解剖特征。棘状椎骨长期以来被视为四足动物的原祖形态,脊柱椎骨中具有背侧置入的椎弓和神经棘,即前腹置入的间椎体和和成对的后背侧置入的半侧椎骨体。然而,我们对有关最早四足动物躯干的椎解剖仍所知甚少,因为大多数标本仍然被困在周围基质中,这模糊了重要的

Read More

论文摘要中生代镶嵌踝类主龙表现出了不同的形态和喂养方式,这表明了相当大的生态多样性,然而宏观进化模式仍然尚未被探索。在此,我们以下颌骨作为形态功能的代表,使用了形态学和生物力学差距指标的独特组合来量化生态多样性以及中生代镶嵌踝类主龙的摄食辐射。我们复原了三大主流趋势。首先,晚三叠世镶嵌踝类主龙的多样化

Read More

论文摘要传播相衬同步辐射显微层析(PPC- SRμCT)已被证明用来研究化石是非常适合的。由于化石的埋藏保存,大小,形状和密度范围十分广泛,X射线计算机断层扫描协议正为此不断发展和完善。在此我们提出了结合过滤高能量多色光束和长距PPC-SRμCT(样品检测:4-16米)的1-h过程以及正规化吸收曲线的

Read More

论文摘要在过去一个世纪中,各种现代类似生物已被用来推断躯干四足动物和他们鱼类祖先运动表现的演变且获得了不同的成功。 在此,我们对这些从软骨鱼类到哺乳动物的现代类似生物进行了系统发育审查,这强调了脊椎动物类群和运动行为的广泛谱系。我们对由水到陆地过渡早期阶段中的现代类似生物背后的利弊也进行了讨论。尤其值

Read More

论文摘要四足动物的起源以及从游泳到步行的转变是陆生脊椎动物进化和多样化的一个关键步骤。在此期间,四肢的进化,尤其是关节的专门分化和控制运动的结构,从根本上改变了早期四足动物的行动方式。尽管如此,很少有人了解早期四足动物肢体解剖学的功能性后果以及该解剖学如何影响脊椎动物在该进化的非常关键阶段中的运动能力

Read More

AbstractRegional variation in the axial skeleton of pinnipeds (seals and walruses) and its correlation with aquatic locomotory behaviour is examined us

Read More

AbstractVariation in modern crocodilian and extinct thalattosuchian crocodylomorph skull morphology is only weakly correlated with phylogeny, implying

Read More

AbstractSkull shape variation in thalattosuchians is examined using geometric morphometric techniques in order to delineate species, especially with re

Read More