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Fissure deposits are notoriously difficult to date. But, determination of the age of assemblages they contain is crucial for the evolutionary conclusions based on them. The early Mesozoic karst infillings within the Lower Carboniferous limestone of the locality Czatkowice 1 (Southern Poland) containing a diverse terrestrial microvertebrate assemblage (see Borsuk−Białynicka et al. 1999 for review) were originally thought to be most likely Late Permian to Early Triassic in age. Subsequent study of the assemblage containing procolophonids, prolacertiforms, basal lepidosauromorphs, a basal archosaur and small amphibians (including a pre−frog) showed that it is Early Triassic, most probably Late Olenekian, in age because of the advanced dentition pattern of the procolophonids. The discovery of tooth plates of the lungfish Gnathorhiza, known to range from the Induan into early Late Olenekian (Vetlugian Superhorizon to Fedorovskian Horizon of the regional scheme) in Eastern Europe, has further enhanced the dating. The combination of procolophonid and dipnoan evidence now appears to restrict the age of the Czatkowice 1 assemblage to the Early Olenekian.
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Basal Archosauriformes had a wide geographic distribution through the Lower to Middle Triassic. Osmolskina czatkowiensis gen. et sp. nov. from Early Olenekian karst deposits at Czatkowice, west of Cracow, provides the first record from Poland. The reconstructed skull and attributed postcranial elements show a morphology closely resembling that of the Early Anisian African genus Euparkeria Broom, 1913, while differing at generic level. Both genera display the same mosaic of plesiomorphic and apomorphic character states, but share no unique apomorphic character state. They might thus be combined in the family Euparkeriidae Huene, 1920, but could also constitute two plesions of the same grade lying just below the Archosauria + Proterochampsidae node. Currently, Euparkeriidae remains monotypic because no other genus can be assigned to it with confidence. Until this problem is resolved, the term “euparkeriid” essentially denotes a grade of Lower to Middle Triassic non−archosaurian archosauriforms that are more derived than proterosuchid grade taxa, but lack the specializations of either erythrosuchids or proterochampsids. They were probably Pangaean in their distribution.
The scapulocoracoid of Czatkobatrachus polonicus Evans and Borsuk−Białynicka, 1998, a stem−frog from the Early Triassic karst locality of Czatkowice (Southern Poland), is described. The overall type of scapulocoracoid is plesiomorphic, but the subcircular shape and laterally oriented glenoid is considered synapomorphic of Salientia. The supraglenoid foramen is considered homologous to the scapular cleft of the Anura. In Czatkobatrachus, the supraglenoid foramen occupies an intermediate position between that of the early tetrapod foramen and the scapular cleft of Anura. The cleft scapula is probably synapomorphic for the Anura. In early salientian phylogeny, the shift in position of the supraglenoid foramen may have been associated with an anterior rotation of the forelimb. This change in position of the forelimb may reflect an evolutionary shift from a mainly locomotory function to static functions (support, balance, eventually shock−absorption). Laterally extended limbs may have been more effective than posterolateral ones in absorbing landing stresses, until the specialised shock−absorption pectoral mechanism of crown−group Anura had developed. The glenoid shape and position, and the slender scapular blade, of Czatkobatrachus, in combination with the well−ossified joint surfaces on the humerus and ulna, all support a primarily terrestrial rather than aquatic mode of life. The new Polish material also permits clarification of the pectoral anatomy of the contemporaneous Madagascan genus Triadobatrachus.
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