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terça-feira, 30 de junho de 2015

[Paleontology • 2015] Collinsium ciliosum • A Superarmored Lobopodian from the Cambrian of China and Early Disparity in the Evolution of Onychophora


Collinsium ciliosum 
Yang, Ortega-Hernández, Gerber, Butterfield, Hou, Lan & Zhang, 2015
 doi: 10.1073/pnas.1505596112

Collinsium ciliosum, a Collins' monster-type lobopodian from the early Cambrian Xiaoshiba biota of China.
— Jie Yang/Javier Ortega-Hernández 


Significance

Paleozoic lobopodians constitute a diverse assemblage of worm-like organisms that are known from various exceptional fossil deposits and were among the earliest animals to develop skeletonized body parts for protection. Here, we describe Collinsium ciliosum gen. et sp. nov., an armored lobopodian from the early Cambrian Xiaoshiba Lagerstätte (South China). Collinsium belongs to an extinct clade of superarmored lobopodians characterized by supernumerary dorsal spines, and specialized limbs for filter feeding; collectively, these fossil taxa represent a well-defined group within the lineage leading to extant velvet worms (Onychophora). Despite their greater morphological variety and appendage complexity compared with other lobopodians and extant velvet worms, Collinsium and its close relatives embodied a unique, yet ultimately failed, autoecology during the Cambrian explosion.

Abstract
We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.
Kaywords: Collins’ monster, Xiaoshiba Lagerstätte, Cambrian explosion, evolution, phylogeny

A graphical depiction of the morphology of ancient onychophorans. X denotes unavailable or incomplete limb data for the taxon; dashed line indicates morphospace distribution for all members of stem group Onychophora.
— Javier Ortega-Hernández
Jie Yang, Javier Ortega-Hernández, Sylvain Gerber, Nicholas J. Butterfield, Jin-bo Hou, Tian Lan, and Xi-guang Zhang. 2015. A Superarmored Lobopodian from the Cambrian of China and Early Disparity in the Evolution of Onychophora. PNAS. doi: dx.doi.org/10.1073/pnas.1505596112

Spiky monsters: New species of 'super-armored' worm discovered http://bit.ly/1Hk1cGR
via @Cambridge_Uni @EurekAlertAAAS 
Armored Spiky Worm Had 30 Legs, Will Haunt Your Nightmares https://shar.es/1qC293 via @LiveScience

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