Topic
Phyllolepida
About: Phyllolepida is a research topic. Over the lifetime, 8 publications have been published within this topic receiving 182 citations.
Papers
TL;DR: The level of preservation in C. mclachlani provides the basis for a reinterpretation of phyllolepid anatomy and function and consideration of visceral and neurocranial characters supports the hypothesis that placoderms are the sister group to remaining gnathostomes.
Abstract: Remarkably preserved specimens of Cowra- lepis mclachlani Ritchie, 2005 (Proc Linn Soc NSW 126:215-259) (Phyllolepida, Placodermi) represent a unique ontogenetic sequence adding to our understanding of anat- omy, function, and phylogeny among basal jawed verte- brates (gnathostomes). A systematic review demonstrates that the Phyllolepida are a subgroup of the Arthrodira. Con- sideration of visceral and neurocranial characters supports the hypothesis that placoderms are the sister group to remaining gnathostomes. Placoderms possess, as adult ple- siomorphic features, a number of characters that are only seen in the development of extant gnathostomes—a pera- morphic shift relative to placoderms. Developmental evi- dence in vertebrates leads to a revised polarity of character transitions. These include 1) hyomandibula-neurocranium and ventral parachordal-palatoquadrate articulations (ver- tebrate synapomorphies); 2) jointed pharynx, paired basi- branchials, anterior ethmoidal-palatoquadrate articulation, short trabeculae cranii, and anterior and posterior neuro- cranial fissures (gnathostome synapomorphies); and 3) fused basibranchials, dorsal palatoquadrate-neurocranium articulation, loss of the anterior neurocranial fissure, elon- gated trabeculae cranii, and transfer of the ventral para- chordal-palatoquadrate articulation to the trabeculae (crown group gnathostomes). The level of preservation in C. mclachlani provides the basis for a reinterpretation of phyl- lolepid anatomy and function. Cowralepis mclachlani pos- sesses paired basibranchials allowing the reinterpretation of the visceral skeleton in other placoderms. Mandible depression in C. mclachlani follows an osteichthyan pattern and the ventral visceral skeleton acts as a functional unit. Evidence for hypobranchial musculature demonstrates the neural crest origin of the basibranchials and that Cowrale- pis was a suction feeder. Finally, the position of the visceral skeleton relative to the neurocranium in placoderms paral- lels the condition in selachians and osteichthyans, but dif- fers in the elongation of the occiput. The cucullaris fossa of placoderms (interpreted as a site of muscle attachment) is shown to represent, in part, the parabranchial chamber. J. Morphol. 270:775-804, 2009. 2009 Wiley-Liss, Inc.
39 citations
TL;DR: Gavinaspis convergens, a new genus and species of the Phyllolepida, is described on the basis of skull remains from the Late Lochkovian of Qujing, South China, and corroborates the palaeogeographic proximity between Australia and South China during the Devonian Period.
Abstract: Gavinaspis convergens, a new genus and species of the Phyllolepida (Placodermi: Arthrodira), is described on the basis of skull remains from the Late Lochkovian (Xitun Formation, Early Devonian) of Qujing (Yunnan, South China). This new form displays a mosaic of characters of basal actinolepidoid arthrodires and more derived phyllolepids. A new hypothesis is proposed concerning the origin of the unpaired centronuchal plate of the Phyllolepida by a fusion of the paired central plates into one single dermal element and the loss of the nuchal plate. A phylogenetic analysis suggests the position of Gavinaspis gen. nov. as the sister group of the Phyllolepididae, in a distinct new family (Gavinaspididac fam. nov.). This new form suggests a possible Chinese origin for the Phyllolepida or that the common ancestor to Phyllolepida lived in an area including both South China and Gondwana, and in any case corroborates the palaeogeographic proximity between Australia and South China during the Devonian Period.
33 citations
TL;DR: In this article, the Aztec Siltstone fish fauna is described as Austrophyllolepis quiltyi sp. nov., A. A. youngi, Plachelpis tingeyi sp., and phyllolepid indet.
Abstract: Phyllolepid placoderm remains from the Aztec Siltstone fish fauna are described as Austrophyllolepis quiltyi sp. nov., Austrophyllolepis cf. A. youngi, Placolepis tingeyi sp. nov., and phyllolepid indet. The new Antarctic species of two genera previously only known from Australia reinforce evidence from other fish taxa of close biogeographic affinity, as part of the eastern margin of Palaeozoic Gondwana. At least three genera and four species gives the Aztec Siltstone fish fauna the most diverse phyllolepid assemblage known, and probably the oldest documented so far (?late Middle Devonian). Specimens of Austrophyllolepis from the type locality at Mount Howitt, Victoria, are refigured for comparison with the Antarctic species. The order Phyllolepida is a key group for understanding Devonian vertebrate biogeography and palaeogeography, with a unique disjunct distribution in both time and space between the Southern and Northern hemispheres. Phyllolepids document one of the major dispersal events in early vertebrate history, which approximately coincided with the Frasnian–Famennian boundary mass extinction during the Late Devonian.
29 citations
TL;DR: A recent paper by Gross as discussed by the authors deals among other matters with the nature of the Antiarch pectoral limbs, and since my own conclusions partly support and partly oppose his very interesting hypothesis, it seems desirable to discuss separately the nature and possible evolution and morphogenesis of these unique vertebrate appendages.
Abstract: Within the last twenty years our knowledge of the structure and distribution of the armoured Placodermi (including Arthrodira, Ptyctodonta, Phyllolepida, Macropetalichthyida, Rhenanida, and Antiarcha) has increased tremendously. The writer is engaged on a morphogenetic analysis of the group, early publication of which is uncertain. A recent paper by Gross (1941) deals among other matters with the nature of the Antiarch pectoral limbs, and since my own conclusions partly support and partly oppose his very interesting hypothesis, it seems desirable to discuss separately the nature and possible evolution and morphogenesis of these unique vertebrate appendages. To do so it is necessary to review the paired limbs of other placoderms and of Acanthodii, with special reference to their functional significance.
20 citations
20 Mar 2005
TL;DR: A new phyllolepid placoderm occurrence from a low level in the Dulcie Sandstone, Georgina Basin, Northern Territory, lies about 200 metres stratigraphically above an older fish assemblage containing Wuttagoonaspis as mentioned in this paper.
Abstract: A new phyllolepid placoderm occurrence from a low level in the Dulcie Sandstone, Georgina Basin, Northern Territory, lies about 200 metres stratigraphically above an older fish assemblage containing Wuttagoonaspis. A new species Austrophyllolepis dulciensis is characterised by an unusually broad anterior ventrolateral plate. The stratigraphic range of other species in this genus from southeastern Australia and Antarctica suggest a Givetian-Frasnian age. Early members of the order Phyllolepida are endemic to east Gondwana, and other phyllolepids of similar age occur in Turkey and Venezuela. In the Northern Hemisphere (Europe, Russia, Greenland, North America) phyllolepids are restricted to the latest Devonian stage (Famennian). This disjunct space-time distribution for the group supports a Gondwanan origin for the Phyllolepida, and later access to northern landmasses resulting from closure of the ocean between Gondwana and Laurussia at or near the Frasnian-Famennian boundary.
14 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2009 | 1 |
| 2008 | 2 |
| 2005 | 4 |
| 1947 | 1 |