THE TRACE-FOSSIL RECORD OF MAJOR EVOLUTIONARY RADIATIONS

2017 ◽  
Author(s):  
Luis A. Buatois ◽  
◽  
Maria Gabriela Mangano
2017 ◽  
Vol 173 ◽  
pp. 96-108 ◽  
Author(s):  
M. Gabriela Mángano ◽  
Luis A. Buatois
Keyword(s):  

Author(s):  
Sören Jensen ◽  
Mary L. Droser ◽  
James G. Gehling
Keyword(s):  

2003 ◽  
Vol 77 (3) ◽  
pp. 576-582 ◽  
Author(s):  
Sally E. Walker ◽  
Steven M. Holland ◽  
Lisa Gardiner

Land hermit crabs (Coenobitidae) are widespread and abundant in Recent tropical and subtropical coastal environments, yet little is known about their fossil record. A walking trace, attributed to a land hermit crab, is described herein as Coenobichnus currani (new ichnogenus and ichnospecies). This trace fossil occurs in an early Holocene eolianite deposit on the island of San Salvador, Bahamas. The fossil trackway retains the distinctive right and left asymmetry and interior drag trace that are diagnostic of modern land hermit crab walking traces. The overall size, dimensions and shape of the fossil trackway are similar to those produced by the modem land hermit crab, Coenobita clypeatus, which occurs in the tropical western Atlantic region. The trackway was compared to other arthropod traces, but it was found to be distinct among the arthropod traces described from dune or other environments. The new ichnogenus Coenobichnus is proposed to accommodate the asymmetry of the trackway demarcated by left and right tracks. The new ichnospecies Coenobichnus currani is proposed to accommodate the form of the proposed Coenobichnus that has a shell drag trace.


1996 ◽  
Vol 70 (1) ◽  
pp. 128-131 ◽  
Author(s):  
Richard J. Twitchett

A new trace fossil from the Lower Triassic of northern Italy is described. It is a sinuous resting trace of a bilaterally symmetrical worm-like animal. The anterior end is characterised by a pair of lateral projections. It most closely resembles an acorn-worm (class Enteropneusta) in morphology. As such, it is the only known resting trace of an acorn-worm from the fossil record.


2021 ◽  
Vol 7 (24) ◽  
pp. eabf2257
Author(s):  
Alan J. S. Beavan ◽  
Davide Pisani ◽  
Philip C. J. Donoghue

Molecular evolutionary time scales are expected to predate the fossil evidence, but, particularly for major evolutionary radiations, they can imply extremely protracted stem lineages predating the origin of living clades, leading to claims of systematic overestimation of divergence times. We use macroevolutionary birth-death models to describe the range of total-group and crown-group ages expected under constant rates of speciation and extinction. We extend current predictions on origination times for crown- and total-groups, and extinction of stem-groups, demonstrating that there is broad variance in these predictions. Under constant rates of speciation and extinction, we show that the distribution of expected arthropod total-group ages is consistent with molecular clock estimates. The fossil record cannot be read literally, and our results preclude attempts to interpret the antiquity of clades based on the co-occurrence of stem- and crown-representatives.


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