Plectronoceratids (Cephalopoda) from the latest Cambrian at Black Mountain, Queensland, reveal complex three-dimensional siphuncle morphology, with major taxonomic implications

PeerJ, Journal Year: 2024, Volume and Issue: 12, P. e17003 - e17003

Published: Feb. 29, 2024

The Plectronoceratida includes the earliest known cephalopod fossils and is thus fundamental to a better understanding of origin early evolution this group molluscs. bulk described material comes from late Cambrian Fengshan Formation in North China with isolated occurrences South China, Laurentia, Kazakhstan Siberia. Knowledge their morphology taxonomy limited that most specimens were only studied as longitudinal sections, which are prone misinterpretations due variations plane section. We describe more than 200 new specimens, exceeds entire hitherto published record plectronoceratids. was collected by Mary Wade colleagues during 1970s 1980s, lower Ninmaroo at Black Mountain (Mount Unbunmaroo), Queensland, Australia. Despite collecting effort, diverse notes incomplete drafts, never before her death 2005. provide novel insights into three-dimensional siphuncle based on abundant material, prompting general revision order Plectronoceratida. Sinoeremoceras marywadeae sp. nov. numerous, well-preserved allowing investigation ontogenetic trajectories intraspecific variability, turn enables improved interpretations morphology. S. other plectronoceratids characterised highly oblique segments, an elongated middorsal portion septal neck (= flap) laterally expanded segments extend dorsally relative flap siphuncular bulbs). show complex structure has caused problems interpretation because it mainly leading impression there large differences between supposed species. revise Protactinoceratida families Protactinoceratidae Balkoceratidae junior synonyms Plectronoceratidae, respectively. reduce number valid genera eighteen (including one genus formerly classified ellesmeroceratid) three: Palaeoceras Flower, 1954, Plectronoceras Kobayashi, 1935 1933. accept 10 species 68 previously established may be assigned. contains 8 plus Two species, referred ellesmeroceratid genera, transferred Sinoeremoceras. This revised scheme groups distinct geographically stratigraphically separated reflects biological realities removes bias preparation techniques. remains important containing highest diversity likely centre diversification.

Language: Английский

Resurgence of cloudinomorph fossils with possible cnidarian affinity at the peak of the Cambrian Explosion (Cambrian Series 2, Stage 3) in southern Shaanxi, China

Papers in Palaeontology, Journal Year: 2024, Volume and Issue: 10(5)

Published: Sept. 1, 2024

Abstract During the Precambrian–Cambrian transition, tubicolous animals were prevalent among small shelly fossils. These include oldest‐known skeletal fossil Cloudina from terminal Ediacaran, and anabarites hyoliths early Cambrian; considered to be possible annelids, cnidarians, molluscs, respectively. Tubular fossils have important bio‐stratigraphic significance during this period, their diversity evolutionary radiation trend herald Cambrian explosion. However, relative morphological simplicity of these lack preserved soft‐body information has resulted in poor taxonomic constraints. Here, numerous tubular exhibiting multi‐stage cylindrical or conical cups recovered middle–upper Guojiaba Formation Series 2, Stage 3, Mianxian, South China. One new genus ( Mianxiantubus ) three species M. cyathiformis , M . obconicus varius established accommodate affinities remain contentious undetermined been tentatively ascribed Cnidaria. The morphology growth patterns suggest a close relationship with cloudinomorph fossils, although it is notably distinct quintessential cloudinids owing presence transverse septa. Moreover, many other same level, which may extend overlying Xiannvdong (Stage 3), co‐occurring archaeocyathids. This suggests that organisms continued diversify occupied specific ecological niches even peak phase explosion, dominated by bilateral epifaunal vagrants.

Language: Английский

Cephalopods of the San José Formation of Peru (Floian, Early Ordovician) and their paleogeographic significance

Journal of Paleontology, Journal Year: 2024, Volume and Issue: unknown, P. 1 - 13

Published: Dec. 9, 2024

Abstract The existence of Ordovician Peruvian cephalopods has been known since at least the 1910s. However, they have not effectively documented previously with only a few described taxa listed in open nomenclature. Here, we describe cephalopod assemblage finest taxonomic level possible. specimens were collected from Floian section ( Baltograptus minutus graptolite Zone) San José Formation Kimbiri area, northwest Cuzco (= Cusco), and along Inambari River, southeastern Peru. dark mudstone-siltstone was deposited within Central Andean Basin. contains five species small orthoceracones belonging to four families three orders, consisting one indeterminate dissidocerid, bathmoceratid Saloceras sp.), rioceratid Rioceras ? two baltoceratids Annbactroceras grecicostatum (Kobayashi, 1937), Bactroceras cocafolium new species. dominance is typical for early Paleozoic pelagic assemblages. One species, A . , elsewhere other indicate peri-Gondwana-Avalonia paleogeographical relationship fauna, which consistent published data brachiopods trilobites. UUID: http://zoobank.org/f5cc9686-75f2-46de-bdd9-f279e3b45677

Language: Английский