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A crown‐group demosponge from the early C ambrian S irius P asset B iota, N orth G reenland
Author(s) -
Botting Joseph P.,
Cárdenas Paco,
Peel John S.
Publication year - 2015
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/pala.12133
Subject(s) - sponge spicule , paleontology , biology , sponge , lineage (genetic) , spicule , phylogenetic tree , biochemistry , gene
Calibration of the divergence times of sponge lineages and understanding of their phylogenetic history are hampered by the difficulty in recognizing crown versus stem groups in the fossil record. A new specimen from the lower C ambrian (Series 2, Stage 3; approximately 515 Ma) S irius P asset B iota of N orth G reenland has yielded a diagnostic spicule assemblage of the extant demosponge lineages H aploscleromorpha and/or H eteroscleromorpha. The specimen has disarticulated approximately in situ , but represents an individual sponge that possessed monaxon spicules combined with a range of slightly smaller sigma, toxa and unique spiral morphologies. The combination of spicule forms, together with their relatively large size, suggests that the sponge represents the stem lineage of H aploscleromorpha + H eteroscleromorpha. This is the first crown‐group demosponge described from the early C ambrian and provides the most reliable calibration point currently available for phylogenetic studies.