A defining feature of tetrapod evolutionary origins is the transition from fish fins to limbs. major change during this appearance autopod (hands, feet), which comprises two distinct regions, wrist/ankle and digits. When first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before full complement bones. Early wrists/ankles, including those with a bones, also show sharp pattern discontinuity between proximal elements distal elements. This suggests presence...

Placoderms are extinct jawed fishes of the class Placodermi and basal among vertebrates. It is generally thought that teeth absent in placoderms phylogenetic origin occurred after evolution jaws. However, we now report presence tooth rows more derived placoderms, arthrodires. New composed gnathostome-type dentine develop at specific locations. Hence, it appears these placoderm regulated as other Because development occurs only forms suggest evolved least twice, through a mechanism convergent...

Significance Oral teeth and skin denticles share a deep, 450-million-year-old, evolutionary relationship among vertebrates. We investigate how evolved from simpler using sharks as an developmental model. The striking ability of shark to regenerate rapidly continuously is not shared by denticles, we suggest that this difference related the tooth-specific expression stem cell factor sox2. show epithelial progenitors dentition remarkable with taste buds. arose combining gene regulatory network...

ABSTRACT Newly discovered pelvic and reproductive structures within placoderms, representing some of the most crownward members gnathostome stem group basal jawed vertebrates, challenge established ideas on origin girdle complexity. Here we critically review previous descriptions in placoderms reinterpret morphology region arthrodires ptyctodonts, particular position fin relationship male clasper to girdle. Absence clear articular surfaces Arthrodira, along with evidence from Ptyctodontida,...

Shark and ray (elasmobranch) dentitions are well known for their multiple generations of teeth, with isolated teeth being common in the fossil record. However, how diverse characteristic elasmobranchs form is still poorly understood. Data on development maintenance dental patterning this major vertebrate group will allow comparisons to other morphologically taxa, including bony fishes, order identify shared pattern characters dentition as a whole. especially lacking from Batoidea (skates...

Mandibles represent a key evolutionary innovation that enabled jawed vertebrates to adapt and diversify in response range of food sources. Using phylogenetic comparative approach, we explore the phenotypic disparity mechanical properties lower jaw Pelagiaria, morphologically diverse but relatively small clade open-ocean fishes which are hypothesized have radiated near Cretaceous/Paleogene (K/Pg) mass extinction event. We found body elongation diet not significantly correlated with shape,...

A rich fossil record of teeth shows that many living shark families' origins lie deep in the Mesozoic. Skeletal fossils sharks to whom these belonged are far rarer and when they preserved often flattened, hindering understanding evolutionary radiation groups. Here we use computed tomography describe two articulated Upper Cretaceous skeletons from Chalk UK preserving three-dimensional neurocrania, visceral cartilages, pectoral vertebrae. These display skeletal anatomies characteristic...

Teleost fishes comprise approximately half of all living vertebrates. The extreme range diversity in teleosts is remarkable, especially, extensive morphological variation their jaws and dentition. Some the most unusual dentitions are found among members highly derived teleost order Tetraodontiformes, which includes triggerfishes, boxfishes, ocean sunfishes, pufferfishes. Adult pufferfishes (Tetraodontidae) exhibit a distinctive parrot-like beaked jaw, forming cutting edge, unlike any other...

Abstract The Late Cretaceous (Cenomanian–Maastrichtian) Chalk Group and Eocene (Ypresian) London Clay Formation are two British marine deposits that yield globally significant assemblages of fossil actinopterygian (ray-finned) fishes. Materials from these units, especially the Chalk, featured prominently in work Arthur Smith Woodward. Here we summarize history study fossils Clay, review their geological palaeoenvironmental context provide updated faunal lists. remarkable for preserving...

The dentitions of extant fishes and land vertebrates vary in both pattern type tooth replacement. It has been argued that the common ancestral condition likely resembles nonmarginal, radially arranged files arthrodires, an early group armoured fishes. We used synchrotron microtomography to describe fossil so-called acanthothoracids, most phylogenetically basal jawed with teeth, belonging genera Radotina, Kosoraspis, Tlamaspis (from Early Devonian Czech Republic). Their differ fundamentally...

Attempts to explain the origin and diversification of vertebrates have commonly invoked evolution feeding ecology, contrasting passive suspension invertebrate chordates larval lampreys with active predation in living jawed vertebrates. Of extinct jawless that phylogenetically intercalate these groups, apparatus is well-preserved only early diverging stem-gnathostome heterostracans. However, its anatomy remains poorly understood. Here, we use X-ray microtomography characterize pteraspid...

Abstract A new member of the Tristichopteridae (=Eusthenopteridae), Mandageria fairfaxi gen. et sp. nov., is described from Late Devonian (Famennian) Mandagery Sandstone outcropping near Canowindra, NSW, Australia. It represented by several complete or partial heads and bodies, preserved as natural moulds. shares derived characters with Famennian tristichopterid Eusthenodon wängsjöi East Greenland; pineal plate series large kite-shaped posterior to middle parietals, intertemporal does not...

ABSTRACT A new tristichopterid, Cabonnichthys burnsi gen. et sp. nov. from the Upper Devonian Mandagery Sandstone near Canowindra, New South Wales, Australia, is second tristichopterid to be described this locality. The first, Mandageria fairfaxi, was interpreted as sister group of Laurussian taxon Eusthenodon. similar these two taxa in possessing a posterior supraorbital extending ventrally behind orbit exclude postorbital orbital margin, posteriorly positioned pineal surrounded by kite or...

The Upper Devonian fish fauna from near Canowindra, New South Wales, occurs on a single bedding plane, and represents the remains of one palaeocommunity. Over 3000 have been collected, predominantly antiarchs Remigolepis walkeri Johanson, 1997a, Bothriolepis yeungae n.sp. nature preservation Canowindra suggests these became isolated in an ephemeral pool water that subsequently dried within relatively short space time. This event occurred non-reproductive period, which, along with predation...

SUMMARY Although the lungfish (Dipnoi) belong within Osteichthyes, their dentitions are radically different from other osteichthyans. Lungfish also show a uniquely high structural disparity during early evolution of group, partly owing to independent variation odontogenic and odontoclastic processes that tightly stereotypically coordinated in We present phylogenetic analysis lungfishes incorporating novel approach coding these process characters preference resultant adult dental morphology....

A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering external skin denticles (placoid scales), but less well understood the wide morphological diversity that these can show. Some more unusual are tooth-like structures associated with elongate cartilaginous rostrum 'saw' in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and fossil Sclerorhynchoidea (Batoidea). Comparative topographic developmental studies...