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A eucrustacean from the C ambrian ‘ O rsten’ of S weden with epipods and a maxillary excretory opening
Author(s) -
Waloszek Dieter,
Maas Andreas,
Olesen Jørgen,
Haug Carolin,
Haug Joachim T.
Publication year - 2014
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.12094
Subject(s) - appendage , anatomy , excretory system , biology , crustacean , maxilla , trunk , extant taxon , paleontology , zoology , evolutionary biology , ecology
Abstract The C ambrian species P aulinecaris siveterae n. gen. n. sp., known from two trunk fragments, represents the first record of epipods (serving as gills and osmoregulatory structures) in a crustacean from the S wedish ‘ O rsten’. Moreover, it is the first report of the maxillary excretory opening of a crustacean based on C ambrian material of ‘ O rsten’‐type preservation. One specimen comprises the maxillary segment with an appendage and several thoracic segments with parts of their limbs; a second specimen is a fragment possibly of a more posterior part of the trunk. As in other known small eucrustaceans, the tergites of the new species lack prominent tergopleurae, so that the limbs insert directly ventral to the tergal margins. Limb preservation includes the maxilla and several thoracopods, all possessing a prominent, fleshy basipod with six setose endites along their median rim distally to the proximal endite. The presence of long and prominent limbs of P . siveterae suggests that it had good swimming ability, while the slight C ‐like curvature of their basal limb part, basipod, indicates involvement of the limbs also in so‐called ‘sucking chambers’ for suspension feeding coupled with locomotion. The estimated total length of P . siveterae, 2–3 mm, is comparable to that of extant cephalocarids, but its appendages are twice as long and wide. The limbs of P . siveterae also differ in size and armature from extant eucrustaceans as well as early representatives of this group known from the ‘ O rsten’ assemblages. The general morphology of the limbs, for example in having a fleshy and C ‐shaped basipod with several setae‐bearing endites medially, identifies P . siveterae as an entomostracan eucrustacean, but a lack of further details precludes its affinity with any of the in‐group taxa. Three epipods on the outer edge of the basipod, as in P . siveterae , are also known from the C ambrian eucrustacean Y icaris dianensis from C hina and early ontogenetic stages of extant fairy shrimps ( A nostraca); their adult stages have two epipods. This hints at an original number of three epipods in the ground pattern of E ntomostraca, but some uncertainty remains with regard to the eucrustacean ground pattern because M alacostraca possess a maximum number of two.