First report of paired ventral endites in a hurdiid radiodont

Zoological Letters

Table 1 Comparison of frontal appendage characters in select hurdiid and tamisiocaridid genera

	Shaft endite(s)	Endite morphology and orientation (Fig. 1d, e or Fig. 6b)	Auxiliary spines/ setae	#pd with elongate endites in d.a.r.	Shape of arthrodial membrane	Refs
Hurdiidae
Aegirocassis	Elongate, bears proximally facing auxiliary spines	1e	Dist	5	Straight	[10]
Hurdia	Reduced, distally pointing	1e	Dist	5	Straight	[18, 24, 29]
Pahvantia	Two, recurved, with auxiliary spines on distal margin	1e	Dist	5	Straight	[16]
Peytoia	Absent	1e	Dist	5	Straight	[29]
Peytoia? (?Laggania of Daley & Budd 2010)	Elongate, with no auxiliary spines	1e	Dist	5	Straight	[22]
Stanleycaris	Very reduced, distally pointing	1e	Dist	5	Straight	[30, 37]
Ursulinacaris	Elongate, with no auxiliary spines, distally pointing	6b	Dist	5	Straight	this study
Tamisiocarididae
Tamisiocaris	Elongate spine with no auxiliary spines	1d	Dist and prox^a	17	Triangular	[11, 23]
Anomalocaris briggsi	Wide and short, bearing auxiliary spines on distal and proximal margins	1d	Dist and prox	12	Triangular	[7]

^aNo auxiliary spines are known in Tamisiocaris from the Kinzers Formation, however this could be the result of taphonomic removal [28]. Abbreviations: d.a.r distal articulated region, dist distal margin of endite, prox proximal margin of endite, Refs references

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