Braincase evolution in suchian archosaurs (Reptilia: Diapsida): evidence from the rauisuchian Batrachotomus kupferzellensis

The osteology of an almost complete braincase of the rauisuchian archosaur Batrachotomus kupferzellensis Gower from the Middle Triassic of Germany is described. There is a possibly discrete epiotic ossification, the metotic fissure is undivided by bone (i.e. there is a metotic foramen), the medial wall of the otic capsule is mostly ossified, the cerebral branch of the internal carotid artery entered the lateral surface of the parabasisphenoid, the ventral ramus of the opisthotic is more prominent laterally than a strong subvertical ridge on the exoccipital and basioccipital that lies posterior to the external foramen for the hypoglossal nerve, and the perilymphatic foramen faces away from the otic capsule in a posterior direction. Braincase morphology in the rauisuchians Saurosuchus galilei , Postosuchus kirkpatricki, and Tikisuchus romeri is reviewed. A matrix of 27 braincase characters for 12 archosaurian taxa is analysed. The most parsimonious hypothesis is consistent with the currently orthodox view of archosaurian phylogeny, except in that aetosaurians are more closely related to crocodylomorphs than is any rauisuchian. This phylogeny is used in a brief interpretation of the evolution of derived braincase features present in extant crocodilians. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society , 2002, 136 , 49–76.     

Phylogenetic implications of the morphology of the braincase of caecilian amphibians (Gymnophiona)

Caecilian morphology is strongly modified in association with their fossorial mode of life. Currently phylogenetic analyses of characters drawn from the morphology of caecilians lack resolution, as well as complementarity, with results of phylogenetic analyses that employ molecular data. Stemming from the hypothesis derived from the mammal literature that the braincase has the greatest potential (in comparison to other cranial units) to yield phylogenetic information, the braincase and intimately associated stapes of 27 species (23 genera) of extant caecilians were examined using images assembled via microcomputed tomography. Thirty‐four new morphological characters pertaining to the braincase and stapes were identified and tested for congruence with previously recognized morphological characters. The results reveal that when added to previous character matrices, characters of the braincase and stapes resolve generic‐level relationships in a way that is largely congruent with the results of molecular analyses. Analysis of a combined data set of molecular and morphological data provides a framework for conducting ancestral character state reconstructions, which resulted in the identification of 95 new synapomorphies for various clades and taxa, 27 of which appear to be unique for the taxa that possess them. Together these data demonstrate the utility of the application of characters of the braincase and stapes for resolving phylogenetic relationships for a group whose morphology is largely confounded by functional modifications. In addition this study provides evidence of the utility of the braincase in resolving problematic morphology‐based phylogeny outside of Amniota, in an amphibian group. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 160–201.     

The braincase and middle ear region of Dendrerpeton acadianum (Tetrapoda: Temnospondyli)

Dendrerpeton acadianum from the Westphalian A (Upper Carboniferous) of Joggins, Nova Scotia, is a phylogenetically and chronologically early temnospondyl. Its external cranial anatomy has been used previously to suggest the presence of a tympanic membrane, and thus of an ear adapted to the perception of airborne sound. However, supporting evidence provided by stapedial and braincase morphology has so far been lacking. The braincase and middle ear region have remained almost wholly unknown. CT scanning and 3-D computer reconstruction of BMNH R.436 have been used to shed light on these important areas. Both stapes prove to be present in the specimen; the right stapes is distorted, but the left stapes lies inside the cranial cavity and is perfectly preserved. The latter resembles the stapes of the relatively few other temnospondyls in which the bone has been described and is most similar to that of Doleserpeton . The morphology and orientation of the stapes provide strong evidence for the presence of an ear adapted to the perception of airborne sound, with similarities to the extant anuran condition. The reconstructed braincase shows a high degree of similarity to that of other adequately known temnospondyls. This gives supporting evidence that D. acadianum is correctly placed in the temnospondyl phylogeny and thus demonstrates one of the earliest hearing systems adapted to the perception of airborne sound that can be homologized with the extant anuran condition.  © 2005 The Trustees of the Natural History Museum, Zoological Journal of the Linnean Society , 2005, 143 , 577−597.     

Disparity and geometry of the skull in Archosauria (Reptilia: Diapsida)

A metric comparison of 155 fossil and extant species in lateral view based on the proportions of three homologous units (braincase, orbit and rostrum) reveals the existence of an archosaurian skull geometry. An empirical morphospace depicting skull proportions shows that the most variable unit is the rostrum. Three skull types based on rostral proportion are proposed: meso-, longi- and brevirostral. These types depend, on one hand, on a direct numerical relationship between the braincase and the orbit, with a mean ratio of 1:1; never surpassing a 2:1 or 1:2 ratio limit. On the other hand, skull types show a significant negative correlation between braincase and rostrum proportions. Close relationships have been obtained between orbit and the rostrum, although with lower significance and a geometric meaning specific to each group. Skull types depend mainly on the proportional relationship between the rostrum and the braincase. Mesorostral types account for more natural occurrences within morphospace, implying a plesiomorphic condition in Archosauria. Skulls with highest longirostral values (flying forms) display a more restrictive braincase–orbit ratio relationship. Brevirostrals are limited to the smallest skull lengths, up to approximately 180 mm. 85% of brevirostral modern birds have altricial post-hatchling development. General allometric pattern is very similar for all sampled archosaurs, although giant taxa (i.e. non-avian theropods) display a different type of skull proportional growth, closer to isometry. Results reveal the existence of a constructional skull geometry, highlighting the importance of the deviance of the structural design from adaptive explanations on craniofacial morphology in macroevolution.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 67–88.     

A review of the platanaceous woods from the Eocene paratropical rainforest of south-east England

Small diameter pyritized axes, commonly referred to as 'twigs', of fossil platanaceous wood are described from the Lower Eocene London Clay Formation of south-east England. These twigs are characterized by solitary vessels with scalariform perforation plates, opposite intervessel pits, and tall, multiseriate rays that dilate in the phloem region. The wood anatomy supports close relationship to members of extant Platanaceae and the material is placed in the organ genus Plataninium Unger erected for fossil woods with close anatomical similarity to Platanus L. This material supplements the fossil record of platanaceous type wood from the Eocene London Clay and documents the first record of Plataninium decipiens Brett in the twig flora.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 181–191.     

A phylogeny of the families of fossil and extant tetraodontiform fishes (Acanthomorpha, Tetraodontiformes), Upper Cretaceous to Recent

A data matrix is presented of 210 morphological characters (mostly osteological, some external) for 20 extant taxa of the ten Recent families of tetraodontiform fishes and 36 fossil tetraodontiforms. The oldest of these are from the Upper Cretaceous (95 Mya); most are from the Lower to Middle Eocene (50–58 Mya). There are two outgroup taxa (a zeiform and a caproid). A cladistic analysis of this matrix for only the extant taxa produced two equally parsimonious trees that call into question the monophyly of some of the previously accepted major higher-level tetraodontiform clades. Inclusion in the analysis of the large number of available fossil taxa helps to resolve relationships between family level clades. The new phylogenetic hypothesis, together with stratigraphic and biogeographical data, is used to discuss scenarios of the origin and evolution of the major clades of the order.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 565−617.     

Functional morphology of neck musculature in the Tyrannosauridae (Dinosauria, Theropoda) as determined via a hierarchical inferential approach

With multiple well-preserved specimens, tyrannosaurid dinosaurs are ideal subjects for exploring the role of the neck for feeding in an extinct amniote clade. Detailed exploration of the morphology of avian and crocodilian neck muscles grounds phylogenetic inference of musculature of tyrannosaurids. Introduced methods of kinematic and physiological inference explicate action and function of tyrannosaurid neck muscles, and the explicit method of extant behavioural interpolation (EBI) allows inference of generalized behaviours. Anteriorly originating craniocervical muscles of tyrannosaurids, and insertions of the neck dorsiflexor m. transversospinalis cervicis, were similar to those of birds, while the major respective head dorsiflexor and lateroflexor, m. transversospinalis capitis and m. longissimus capitis superficialis, resembled their homologues in crocodilians. Because the proposed inferential methods are cumulative and emphasize mutual falsification, behavioural effects of muscle function become immediately testable rather than assumed. Kinematic inference of muscle moment topology, and bracketed and unipolar inference of muscle activity, facilitate EBI of rapid gaze shifts, lateral and sagittal strikes, inertial feeding, and tearing of flesh by specific permutational actions of tyrannosaurid neck muscles. Several examples of EBI are tested further through biomechanical considerations.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 151 , 759–808.