A Devonian predatory fish provides insights into the early evolution of modern sarcopterygians

Machaeridians are Palaeozoic animals that are dorsally armoured with serialized, imbricating shell plates that cover or enclose the body. Prior to the discovery of an articulated plumulitid machaeridian from the Early Ordovician of Morocco that preserved unambiguous annelid characters (segmental parapodia with chaetae), machaeridians were a palaeontological mystery, having been previously linked to echinoderms, barnacles, tommotiids (putative stem-group brachiopods) or molluscs. Although the annelid affinities of machaeridians are now firmly established, their position within the phylum and relevance for understanding the early evolution of Annelida is less secure, with competing hypotheses placing Machaeridia in the stem or deeply nested within the crown group of annelids. We describe a scleritome of Plumulites bengtsoni from the Fezouata Formation of Morocco that preserves an anterior jaw apparatus consisting of at least two discrete elements that exhibit growth lines. Although jaws have multiple independent origins within the annelid crown group, comparable jaws are present only within Phyllodocida, the clade that contains modern aphroditiforms (scaleworms and relatives). Phylogenetic analysis places a monophyletic Machaeridia within the crown group of Phyllodocida in total-group Aphroditiformia, consistent with a common origin of machaeridian shell plates and scaleworm elytrae. The inclusion of machaeridians in Aphroditiformia truncates the ghost lineage of Phyllodocida by almost a hundred million years.

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New information on Lethiscus stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda

Canadian Journal of Earth Sciences ◽

10.1139/e03-023 ◽

2003 ◽

Vol 40 (8) ◽

pp. 1071-1083 ◽

Cited By ~ 28

Author(s):

Jason S Anderson ◽

Robert L Carroll ◽

Timothy B Rowe

Keyword(s):

Computed Tomography ◽

Phylogenetic Analysis ◽

High Resolution ◽

Entire Length ◽

Serial Sectioning ◽

New Classification ◽

High Resolution Computed Tomography ◽

Lower Jaw ◽

New Information

High-resolution computed tomography provides an alternative to serial sectioning and other destructive techniques of studying fossils (data available at http://www.DigiMorph.org). This technology was used to study the oldest aistopod Lethiscus stocki. The fossil is found to have approximately 30 closely spaced teeth on its maxilla and dentary, a short vomer, a palatine running nearly the entire length of the maxilla that is toothed at least posteriorly, and a choana that is located at the premaxillamaxilla suture. It has a lower jaw with a high articlular facet for the quadrate condyle; a lateral fossa for the adductor musculature, superficially similar to the mammalian masseteric fossa; and a sutural pattern that closely resembles that of Oestocephalus. Previously reported pectoral elements are not evident in the scans and may be best interpreted as fractures on the surface of the nodule associated with sedimentary inclusions. Relationships among all relatively complete aistopods were analyzed using parsimony. Two most parsimonious trees were found, differing in the arrangement of the outgroup taxa. Phlegethontia and Pseudophlegethontia are found to be sister taxa to Coloraderpeton and Oestocephalus, with Ophiderpeton and Lethiscus placed as successively more distant taxa. This topology renders Ophiderpetontidae, as previously conceived, paraphyletic. Lethiscus is confirmed to be the most basal aistopod. A new classification of Aistopoda is presented. This study shows that the palatoquadrate of higher aistopods is derived in-group, which is consistent with the trends in aistopods of peramorphosis in the endochondral skeleton and paedomorphosis in the dermal skeleton.

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New mid-Cretaceous cryptic slime mold beetles and the early evolution of Sphindidae (Coleoptera: Cucujoidea)

Arthropod Systematics & Phylogeny ◽

10.3897/asp.79.e72724 ◽

2021 ◽

Vol 79 ◽

pp. 587-597

Author(s):

Yan-Da Li ◽

Erik Tihelka ◽

Zhen-Hua Liu ◽

Di-Ying Huang ◽

Chen‑Yang Cai

Keyword(s):

Phylogenetic Analysis ◽

Fossil Record ◽

Slime Mold ◽

Early Evolution ◽

Calibration Point ◽

Crown Group ◽

Slime Molds ◽

The Family ◽

Group Members

Abstract The cryptic slime mold beetles, Sphindidae, are a moderately diverse cucujoid beetle family, whose members are obligately tied to slime molds throughout their life. The fossil record of sphindid beetles is sparse; stem-sphindids and crown-group members of uncertain systematic placement have been reported from Cretaceous ambers. Here we review the Mesozoic fossil record of Sphindidae and report a new sphindid genus and species, Trematosphindus newtonigen. et sp. nov., from Albian/Cenomanian amber from northern Myanmar (ca. 99 Ma). Trematosphindus is set apart from all other sphindids by the presence of distinct lateral cavities on the anterior pronotal angles. Our phylogenetic analysis identifies Trematosphindus as an early-diverging genus within Sphindidae, sister to the remainder of the family except Protosphindus, or Protosphindus and Odontosphindus. The new fossils provide evidence that basal crown slime mold beetles begun to diversify by the mid-Cretaceous, providing a valuable calibration point for understanding timescale of sphindid co-evolution with slime molds.

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Redescription of Phymolepis cuifengshanensis (Antiarcha: Yunnanolepididae) using high-resolution computed tomography and new insights into anatomical details of the endocranium in antiarchs

10.7287/peerj.preprints.26867 ◽

2018 ◽

Author(s):

Yajing Wang ◽

Min Zhu

Keyword(s):

Computed Tomography ◽

Phylogenetic Analysis ◽

High Resolution ◽

General Pattern ◽

Morphological Data ◽

Internal Cavity ◽

High Resolution Computed Tomography ◽

Early Devonian ◽

Internal Morphology ◽

High Degree

Background. Yunnanolepidoids constitute either the basal-most consecutive segments or the most primitive clade of antiarchs, a highly diversified jawed vertebrate group from the Silurian and Early Devonian periods. Although the general morphology of yunnanolepidoids is well established, their endocranial features remain largely unclear, thus hindering our further understanding of antiarch evolution, and early gnathostome evolution. Phymolepis cuifengshanensis, a yunnanolepidoid from the Early Devonian of southwestern China, is re-described in detail to reveal the information on endocranial anatomy and additional morphological data of head and trunk shields. Methods. We scanned the material of P. cuifengshanensis using high-resolution computed tomography a nd generated virtual restorations to show the internal morphology of its dermal shield. The dorsal aspect of endocranium in P. cuifengshanensis was therefore inferred. The phylogenetic analysis of antiarchs was conducted based on a revised and expanded dataset that incorporates ten new cranial characters. Results. The lateroventral fossa of trunk shield and Chang’s apparatus arethree-dimensionally restored in P. cuifengshanensis. The canal that is positioned just anterior to the internal cavity of Chang’s apparatus, probably corresponds to the rostrocaudal canal of euantiarchs. The endocranial morphology of P. cuifengshanensis corroborates a general pattern for yunnanolepidoids with additional characters distinguishing them from sinolepids and euantiarchs, such as a developed cranio-spinal process, an elongated endolymphatic duct, and a long occipital portion. Discussion. In light of new data from Phymolepis and Yunnanolepis, we summarized the morphology on the visceral surface of head shield in antiarchs, and formulated additional ten characters for the phylogenetic analysis. These cranial characters exhibit a high degree of morphological disparity between major subgroups of antiarchs, and highlight the endocranial character evolution in antiarchs.

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Redescription ofPhymolepis cuifengshanensis(Antiarcha: Yunnanolepididae) using high-resolution computed tomography and new insights into anatomical details of the endocranium in antiarchs

PeerJ ◽

10.7717/peerj.4808 ◽

2018 ◽

Vol 6 ◽

pp. e4808 ◽

Cited By ~ 4

Author(s):

Yajing Wang ◽

Min Zhu

Keyword(s):

Computed Tomography ◽

Phylogenetic Analysis ◽

High Resolution ◽

General Pattern ◽

Morphological Data ◽

Internal Cavity ◽

High Resolution Computed Tomography ◽

Early Devonian ◽

Internal Morphology ◽

High Degree

BackgroundYunnanolepidoids constitute either the most basal consecutive segments or the most primitive clade of antiarchs, a highly diversified jawed vertebrate group from the Silurian and Early Devonian periods. Although the general morphology of yunnanolepidoids is well established, their endocranial features remain largely unclear, thus hindering our further understanding of antiarch evolution, and early gnathostome evolution.Phymolepis cuifengshanensis, a yunnanolepidoid from the Early Devonian of southwestern China, is re-described in detail to reveal the information on endocranial anatomy and additional morphological data of head and trunk shields.MethodsWe scanned the material ofP. cuifengshanensisusing high-resolution computed tomography and generated virtual restorations to show the internal morphology of its dermal shield. The dorsal aspect of endocranium inP. cuifengshanensiswas therefore inferred. The phylogenetic analysis of antiarchs was conducted based on a revised and expanded dataset that incorporates 10 new cranial characters.ResultsThe lateroventral fossa of trunk shield and Chang’s apparatus are three-dimensionally restored inP. cuifengshanensis. The canal that is positioned just anterior to the internal cavity of Chang’s apparatus probably corresponds to the rostrocaudal canal of euantiarchs. The endocranial morphology ofP. cuifengshanensiscorroborates a general pattern for yunnanolepidoids with additional characters distinguishing them from sinolepids and euantiarchs, such as a developed cranio-spinal process, an elongated endolymphatic duct, and a long occipital portion.DiscussionIn light of new data fromPhymolepisandYunnanolepis, we summarized the morphology on the visceral surface of head shield in antiarchs, and formulated an additional 10 characters for the phylogenetic analysis. These cranial characters exhibit a high degree of morphological disparity between major subgroups of antiarchs, and highlight the endocranial character evolution in antiarchs.

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Redescription of Phymolepis cuifengshanensis (Antiarcha: Yunnanolepididae) using high-resolution computed tomography and new insights into anatomical details of the endocranium in antiarchs

10.7287/peerj.preprints.26867v1 ◽

2018 ◽

Author(s):

Yajing Wang ◽

Min Zhu

Keyword(s):

Computed Tomography ◽

Phylogenetic Analysis ◽

High Resolution ◽

General Pattern ◽

Morphological Data ◽

Internal Cavity ◽

High Resolution Computed Tomography ◽

Early Devonian ◽

Internal Morphology ◽

High Degree

Background. Yunnanolepidoids constitute either the basal-most consecutive segments or the most primitive clade of antiarchs, a highly diversified jawed vertebrate group from the Silurian and Early Devonian periods. Although the general morphology of yunnanolepidoids is well established, their endocranial features remain largely unclear, thus hindering our further understanding of antiarch evolution, and early gnathostome evolution. Phymolepis cuifengshanensis, a yunnanolepidoid from the Early Devonian of southwestern China, is re-described in detail to reveal the information on endocranial anatomy and additional morphological data of head and trunk shields. Methods. We scanned the material of P. cuifengshanensis using high-resolution computed tomography a nd generated virtual restorations to show the internal morphology of its dermal shield. The dorsal aspect of endocranium in P. cuifengshanensis was therefore inferred. The phylogenetic analysis of antiarchs was conducted based on a revised and expanded dataset that incorporates ten new cranial characters. Results. The lateroventral fossa of trunk shield and Chang’s apparatus arethree-dimensionally restored in P. cuifengshanensis. The canal that is positioned just anterior to the internal cavity of Chang’s apparatus, probably corresponds to the rostrocaudal canal of euantiarchs. The endocranial morphology of P. cuifengshanensis corroborates a general pattern for yunnanolepidoids with additional characters distinguishing them from sinolepids and euantiarchs, such as a developed cranio-spinal process, an elongated endolymphatic duct, and a long occipital portion. Discussion. In light of new data from Phymolepis and Yunnanolepis, we summarized the morphology on the visceral surface of head shield in antiarchs, and formulated additional ten characters for the phylogenetic analysis. These cranial characters exhibit a high degree of morphological disparity between major subgroups of antiarchs, and highlight the endocranial character evolution in antiarchs.

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