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For the different species described from Orsten sites see also:

1.9. Phosphatocopina Müller, 1964

Due to their bivalve shield, the Phosphatocopina have long been assumed to be ancestral Cambrian ostracodes, a very special maxillopod eucrustacean taxon with bivalved shield and, due to calcite incrustation in the shell cuticle of some groups and, accordingly, a good preservation, a long fossil record of clearly ostacodes into the Ordovician. Until now, some ostracode workers still upheld this wrong idea. ANotehr taxon from the Cambrian with bivalved shield has also been affiliated with phosphatoocopines, the Bradoriida, but which may not even be Euarthropoda: example Kunmingella from Siveter et al. (1996).

Phosphatocopina are up to 5 mm long and can be characterized as the sistergroup of the Eucrustacea within the Labrophora sensu Siveter et al. (2003, see also Maas et al. 2003 and Maas & Waloszek 2005) on the basis of shared apomorphies = synapomorphies with the latter taxon (= autapomorphies of the common stem species):

  • a protopod with a coxa and a basipod in both (and only in) the antenna 2 and the mandible,
  • a labrum as a glandular organ above mouth and at rear of plesiomorphic hypostome,
  • a sternum, as the product of fusion of the sternites of the antennal, mandibular, and maxillulary segments,
  • a pair of paragnaths representing humps on the mandibulary sternite,
  • a setulation on labrum and sternum, serving for food guidance, prevention from food loss, grooming structures.

Autapomorphies of Phosphatocopina:

  • a large bivalved head shield surrounding the sides of the body and enclosing the entire animal, at least until about 1-2 mm long instars
  • shield is a cephalothoraic shield including at least two more of the trunk limb-bearing ssegments
  • a tiny antennula (A1) made of a few articles and having at most a distal truf of 3-4 setae
  • a well-sclerotized hypostome-labrum complex in later larval stages that includes the frontally located median eyes and the insertions of the antennulae
  • three-segmented endopods at most on all post-antennular limbs
  • a trunk fading towards its end.

Time range and geological range: Phosphatocopina is an exclusively early Paleozoic taxon, known already from the Lower Cambrian (Hinz 1987; Siveter et al. 2001, 2003). Hence they represent the oldest undoubted Crustacea ever found in the fossil record (see also Walossek 1993, Walossek & Müller 1997; Maas et al. 2003).

The single specimen with preserved soft cuticle has been assigned to the vestrogothiids by Ingelore Hinz, although there is very little evidence to support this assignment. It is apparently a very early larval stage, if not the first, having a shield of approx. 300 m in length. The specimen shows the large labrum covering the atrium oris and mouth (character developped inside Crustacea), a sternum (= labium, reaching only until mx1, not until mx2, as in crowngroup Crustacea!) with developping paragnath humps (derived from the mandibular sternite, see Walossek 1993 for the morphogenesis of this structure exposed in the larval sequence of Rehbachiella), the soft inner lamella (ventral body wall underneath (inside) the shield, and at least the insertion areas of the four appendages, including the first antenna (a1 missed in the original description of the soft parts of phosphatocopines by Klaus Müller). The soft membrane anterior of the labrum may represent the collapsed eye lobes, as is known from the Middle to late Cambrian phosphatocopines.

A much more detail description of another specimen from Comley was given by Siveter et al. (2001, 2003), who formally named their form as Klausmuelleria salopensis Siveter, Waloszek & Williams, 2003. Their specimen had the limbs preserved which revealed an important feature: the seeconda antenna A2 and the mandible Md werde bother different from the corresponding mibs of the stem taxa but as in eucrustaceans, namely in having a coxa and a basipod which carried the two rami.
All later phosphatocopines, as explained in more detail below, have no subdivision of the protopod in their A2. Even more, their mandibular coxa is huge while a basipod seems to be missing, except of the earliest stages of Vestrogothia. Ontogeny, indeed, demonstrates that the coxa enlarges while the basipod becomes shorter and, eventually is present merely as a single endite at the nbase of the endopod, so easy to be mismatched as a proximal endopodal podomere simply. The exopod, again, arises, just from the "shoulder" of the coxa in late stages, but earlier instars "still" sho a small band representing the out edge of the basipod, which becomes indistinguishably merged into the coxa. The final shape has more of the euarthropod condition of abasipod carrying the rami, but this is a fake. And the origin of the coxa from a proximal endite is beautifully visible in its specific setation pattern consisting of an anterior set, a median spine or tooth row and a posterior set. This triplet may not be original but a feature also of the labrophoran stem species.

Another important feature revealed by these early specimens is the fact that Phosphatocopina hatched as a larva having antennules and three paits of functional limbs. The Phosphatocopina larva contrasts the larvae of the stem taxa, however, in having "already" a labrum, a sternum, paragnath humps, and atrium oris and fine hairs on all parts around the mouth.
Yet, this head larva is clearly different from that of the Eucrustacea in having one limb more. The eucustacean nauplius has only two funcltional post-antennular limbs pairs, but also all labrophopran features, so is more specialized in being a short-head larva. Eucrustacea, furthermore, specialize their fourth head limb into a "mouth part" = maxillula.

Morphology: Charactized by two large lateral shield parts enclosing the body already in the first larva. In adults possibly incrusted by calcium apatite. No compound eyes found in any taxon. Antennula reduuced in length, arising from the flanks of the hypostome-labrum complex, with few terminal setae.

Trunk initially fully missing, in later stages still not much developed. End part unclear, furcal rami possibly present, which then would be a further labrophoran feature. Endopods of biramous limbs three-segmented at most (plesiomorphically, some later taxa have only two segneted endopods on a2 and md).

Life habits: benthic.

Taxa from the Orsten of Sweden: xxxxxx

Taxa worldwide (state 2003): xxxxxxxxx

Affinities: The presence of plesiomorphic characters, such as the postantennular limbs without significant differentiation or the hypostome, but lack (as far as one can estimate it from the incomplete preservation) of a labrum, an atrium oris, paragnaths and other circum-oral structures characteristic of Phosphatocopina and Eucrustacea – together forming the new taxon Labrophora Siveter, Williams & Waloszek, 2003 – are further features placing Cambrocaris clearly in the stem lineage to the Eucrustacea. To this can be added the locomotory antennula, the post-antennular limbs with proximal endites, the exopods being annulated and having an inwards pointing setation and the mouth at the rear of the hypostoma structure rather than proximal to the labrum.

A very special phosphatocopine has been discovered in Middle Cambrian rock from Australia. This form has clearly lost its exopods on all post-antennular limbs (Walossek et al. 1993, see list of references):

Further literature on Klausmuelleria:
Hinz, Ingelore 1987: Lower Cambrian Microfauna of Comley and Rushton, Shropshire/England. Palaeontographica A, 198(1-3), 41-100, pl. 2, 3; pictures shown here are from her plate 3, figs. 1-3
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