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The Phylocode: Beating a dead horse?

100%

Benton M. J.

Acta Palaeontologica Polonica

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2007

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tom 52

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nr 3

The concept of the Phylocode has been evolving for some twenty years, and is supported by Lee and Skinner (2007): I argue against it here. The first issue is stability, and biologists must decide whether they seek rigidity (Phylocode) or flexibility and conservativeness of clade contents (Linnaean codes). Phylocode names for taxa are by definition stable because they are established as labels for clades that are rigidly defined as geometric constructs. But this is not real stability because the species contained within those clades can change dramatically: an example is given where Phylocode practice forces a decision about the name Deinonychosauria, which can contain 20 or 10,000 species depending on which current tree is correct. Linnaean systems offer real stability (= conservativeness + flexibility) where the taxon name can be moved subtly up and down nodes in a tree to keep its association with a particular character or group of species. Proponents of the Phylocode argue that category/rank terms should be dispensed with, and yet they have no need to do this. Everyone accepts that Linnaean ranks are subjective, and yet there is no benefit in abandoning ranks because they have proved to be of such value to users of classifications, and genera and families, for example, act as valuable surrogates for species in large−scale evolutionary and ecological studies. Finally, the Phylocode extends regulation beyond names and their proper use into determining the validity of phylogenetic hypotheses, and this will act as a limit on normal scientific debate.

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Filling the ceratosaur gap: A new ceratosaurian theropod from the Early Cretaceous of Spain

63%

Sanchez-Hernandez B., Benton M. J.

Acta Palaeontologica Polonica

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2014

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tom 59

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nr 3

Ceratosaurian theropods evolved in two bursts, first in the Middle and Late Jurassic and then in the Late Cretaceous, leaving a 20 Myr gap in the Early Cretaceous during which remains are rare. We describe here a new ceratosaurian theropod, Camarillasaurus cirugedae, from fluvial deposits of the Camarillas Formation (lower Barremian, Lower Cretaceous) of Camarillas, Teruel Province, NE Spain. The new theropod is represented by a collection of associated bones, including a tooth, a possible cervical vertebra, two sternal plates, the proximal part of a right tibia, a broken right scapulocoracoid, the incomplete sacrum, five caudal vertebrae, an isolated caudal neural arch, a chevron, an almost complete presacral rib and some fragments of vertebrae, ribs, and other elements. Camarillasaurus is differentiated from other theropods by the extreme depth of the tibia proximal end, and a deep longitudinal groove on the tibia. The new dinosaur is a ceratosaur, phylogenetically close to the base of the clade, and perhaps more derived than the Chinese basal ceratosaur Limusaurus. The new taxon is significant in the evolution of the ceratosaurian dinosaurs, being placed temporally between its more common Jurassic and mid-Upper Cretaceous relatives, and it is one of only a few from Laurasia.

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Diversity in rhynchocephalian Clevosaurus skulls based on CT reconstruction of two Late Triassic species from Great Britain

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Chambi-Trowell S. A. V., Whiteside D. I., Benton M. J.

Acta Palaeontologica Polonica

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2019

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tom 64

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nr 1

Clevosaurus was an early sphenodontian, known from many specimens and species from the Late Triassic and Early Jurassic. Here we describe and compare the cranial morphology of Clevosaurus hudsoni, the type species, and Clevosaurus cambrica, both from the UK, based on digital reconstructions from segmented CT scan data of two skulls. C. hudsoni has been described in some detail, but the CT data reveal new information on cranial anatomy, and C. cambrica is a newly described species for which the CT scans enable us to identify many previously undescribed bones, re-identify bones whose identity had previously been uncertain, and refine certain cranial elements. The near complete preservation of the left side of the skull of C. cambrica, and the preservation of much of the left side of the skull of C. hudsoni, provided us with the opportunity to fully reconstruct both species’ skulls in three dimensions. For the first time, coronoid bones are identified in Clevosaurus species from the British Isles. These two species show the diversity of morphology in the genus Clevosaurus. We provide evidence for two morphotypes of C. hudsoni based on study of the dentary dentition of the syntypes and other attributed specimens.

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Ontogenetic stages of ceratopsian dinosaur Psittacosaurus in bone histology

51%

Zhao Q., Benton M. J., Hayashi S., Xu X.

Acta Palaeontologica Polonica

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2019

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tom 64

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nr 2

The early ceratopsians Psittacosaurus and Protoceratops have provided important information on dinosaurian development because of abundant specimens of adults, subadults, juveniles, and even hatchlings. Here we present new data and methods for identifying key growth stages from bone histology. Previous studies on Psittacosaurus lujiatunensis from the Early Cretaceous Jehol Biota of China did not present in-depth analysis of growth patterns. Based on a histological study of 43 thin sections from 17 individuals of this species, we recognize four histological ontogenetic stages, i.e., hatchling, juvenile, sub-adult, and adult, but no fully-grown stage. We estimate life history and longevity from diaphyseal growth line counts and other features of histology. We show that P. lujiatunensis grew fast in early stages (hatchling, juvenile, and subadult), according to the density of vascular canals and the different type of bone tissue; the deposition of parallel fibred bone tissue in the outer cortex of the subadult stage indicates that growth rate was slowing down. We introduce a new graphical method to estimate the occurrence and volumes of vascular canals from thin sections more accurately than current two-dimensional approaches.

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The fossil record of early tetrapods: Worker effort and the end-Permian mass extinction

51%

Bernard E. L., Ruta M., Tarver J. E., Benton M. J.

Acta Palaeontologica Polonica

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2010

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tom 55

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nr 2

229-239

It is important to understand the quality of the fossil record of early tetrapods (Tetrapoda, minus Lissamphibia and Amniota) because of their key role in the transition of vertebrates from water to land, their dominance of terrestrial faunas for over 100 million years of the late Palaeozoic and early Mesozoic, and their variable fates during the end−Permian mass extinction. The first description of an early tetrapod dates back to 1824, and since then discoveries have occurred at a rather irregular pace, with peaks and troughs corresponding to some of the vicissitudes of human history through the past two centuries. As expected, the record is dominated by the well−sampled sedimentary basins of Europe and North America, but finds from other continents are increasing rapidly. Comparisons of snapshots of knowledge in 1900, 1950, and 2000 show that discovery of new species has changed the shape of the species−level diversification curve, contrary to earlier studies of family−level taxa. There is, however, little evidence that taxon counts relate to research effort (as counted by numbers of publications), and there are no biasing effects associated with differential study of different time intervals through the late Palaeozoic and Mesozoic. In fact, levels of effort are apparently not related to geological time, with no evidence that workers have spent more time on more recent parts of the record. In particular, the end−Permian mass extinction was investigated to determine whether diversity changes through that interval might reflect worker effort: it turns out that most records of early tetrapod taxa (when corrected for duration of geological series) occur in the Lower Triassic.

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Juvenile-only clusters and behaviour of the Early Cretaceous dinosaur Psittacosaurus

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Zhao Q., Benton M. J., Xu X., Sander P. M.

Acta Palaeontologica Polonica

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2014

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tom 59

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nr 4

It has hitherto been hard to prove that any association of juvenile dinosaurs represents original behaviour rather than sedimentary accumulation, and it has been hard also to determine the ages of such juveniles. A previously described specimen, which consists of an “adult” Psittacosaurus with 34 fully articulated juveniles, turns out to be a composite: the “adult” skull probably has been added, and in any case it is below breeding age. Other juvenile-only clusters have been reported, but the best examples that likely reflect behaviour rather than sedimentary accumulation are specimens from the Early Cretaceous Lujiatun beds in NE China, which were entombed beneath pyroclastic flow deposits. A remarkable juvenile-only cluster of Psittacosaurus shows clear evidence of different ages (five 2-year olds and one 3-year old) based on bone histological analysis. These juveniles may have associated together as a close-knit, mixed-age herd either for protection, to enhance their foraging, or as putative helpers at the parental nest.

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A re-evaluation of goniopholidid crocodylomorph material from Central Asia: Biogeographic and phylogenetic implications

51%

Halliday T. J. D., Brandalise de Andrade M., Benton M. J., Efimov M. B.

Acta Palaeontologica Polonica

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2015

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tom 60

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nr 2

Central Asia is a key area for crocodylomorph evolution, lying midway between the highly documented deposits in Europe and North America, but crocodylomorph fossils from this part of the world are rare. Included among these are specimens collected in the 1970s and 1980s by the Soviet-Mongolian Expeditions in the Jurassic and Cretaceous of Mongolia, Tajikistan, and Kazakhstan. Three species, “Sunosuchus” shartegensis, Kansajsuchus extensus, and Turanosuchus aralensis are redescribed and subjected to phylogenetic analysis for the first time. “Sunosuchus” shartegensis and Kansajsuchus are relatively derived goniopholidids, and part of a pan-east-Laurasian radiation of goniopholidids from which the European goniopholidids subsequently radiated. No characters can be used to distinguish “Sunosuchus” shartegensis from “S.” thailandicus; the two species are therefore synonymized. Turanosuchus aralensis is here considered a nomen dubium. Cladistic analysis suggests that Sunosuchus is polyphyletic, indicating a higher degree of diversification than was previously thought, but also pointing to the need for further systematic revision.

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A new basal actinopterygian fish from the Anisian (Middle Triassic) of Luoping, Yunnan Province, Southwest China

33%

Wen W., Zhang Q.-Y., Hu S.-X., Zhou C.-Y., Xie T., Huang J.-Y., Chen Z. Q., Benton M. J.

Acta Palaeontologica Polonica

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2012

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tom 57

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nr 1

The new neopterygian fish taxon Luoxiongichthys hyperdorsalis gen. et sp. nov. is established on the basis of five specimens from the second member of the Guanling Formation (Anisian, Middle Triassic) from Daaozi Quarry, Luoping, Yunnan Province, Southwest China. The new taxon is characterized by the following characters: triangular body outline with a distinct apex located between skull and dorsal fin; free maxilla; slender preopercular almost vertical; three suborbitals; at least eight strong branchiostegals with tubercles and comb−like ornamentation on the anterior margin; clavicles present; two postcleithra; ganoid scales covered by tubercles and pectinate ornamentation on the posterior margin with peg−and−socket structure; hemiheterocercal tail slightly forked. Comparison with basal actinopterygians reveals that the new taxon has parasemionotid−like triangular symplectics, but a semionotid opercular system. Cladistic analysis suggests that this new genus is a holostean, and either a basal halecomorph or basal semionotiform.

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Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity

33%

Wen W., Zhang Q.-Y., Hu S.-X., Benton M. J., Zhou C.-Y., Tao X., Huang J.-Y., Chen Z.-Q.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 1

The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which to− gether show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the ab− dominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previ− ously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especially in the ornament on dermal bones and scales. Acladistic analysis shows that the new taxa are closest relatives to the derived clade Latimerioidei. The relatively high di− versity of coelacanths in the Early Triassic, and adaptations of living Latimeria to low−oxygen conditions, suggests that the group may have included ‘disaster taxa’ that benefited from anoxic and dysoxic ocean conditions in the aftermath of the end−Permian mass extinction.

Ograniczanie wyników

The Phylocode: Beating a dead horse?

Filling the ceratosaur gap: A new ceratosaurian theropod from the Early Cretaceous of Spain

Diversity in rhynchocephalian Clevosaurus skulls based on CT reconstruction of two Late Triassic species from Great Britain

Ontogenetic stages of ceratopsian dinosaur Psittacosaurus in bone histology

The fossil record of early tetrapods: Worker effort and the end-Permian mass extinction

Juvenile-only clusters and behaviour of the Early Cretaceous dinosaur Psittacosaurus

A re-evaluation of goniopholidid crocodylomorph material from Central Asia: Biogeographic and phylogenetic implications

A new basal actinopterygian fish from the Anisian (Middle Triassic) of Luoping, Yunnan Province, Southwest China

Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity