Sphenothallus Hall, 1847, one of the most widely distributed and longest ranging genera in the fossil record, has been documented from all systems of the Paleozoic Erathem except the Permian (Table 1), although it has been stated (e.g., Choi, 1990; Bolton, 1994; Fatka et al., 2012) that the genus also occurs in that system. At present the first appearance of this epibenthic, polypoid medusozoan cnidarian lies in Cambrian Stage 3, while the previously known youngest occurrences are in the Pennsylvanian System. Sphenothallus has been found in numerous formations on all continents except Australia and Antarctica. It occurs in a variety of marine facies ranging from shallow nearshore to deep offshore and has even been found in strata of coastal lacustrine origin, probably as an allochthonous element (Lerner and Lucas, 2011). Many of the rock units known to contain Sphenothallus also contain conulariids (Table 1), an extinct group of marine scyphozoans that may have been closely related to Sphenothallus (Van Iten et al., 1992, 1996). Van Iten et al. (1992) interpreted Sphenothallus as a medusozoan cnidarian of uncertain class-level affinities, but later Dzik et al. (2017) documented internal peridermal structures that may be homologous to similar features in the periderm of coronate scyphozoans (see for example illustrations in Van Iten, 1992, and Van Iten et al., 1996).

Revisiting horseshoe crab fossils from the Middle Triassic (Anisian) Strelovec Formation Konservat-Lagerstätte of Slovenia

Background: To determine whether the presence of two palatal roots in permanent maxillary molars (PMMs) could be predicted by observing dental morphological traits during the clinical examination. Materials and methods: A total of 18 second and 26 third PMMs with two palatal roots (2PR) were examined from the collection of extracted teeth. The reference sample of 44 extracted PMMs with one palatal root was selected such that pairs of morphologically matching PMMs with one and 2PR were formed. The external morphology of these tooth pairs was examined under a stereomicroscope and distinguishing traits were registered. The Fisher’s exact test was applied to examine differences between second and third PMMs. Additionally, the external morphology of 17 PMM with 2PR in 15 patients was analyzed retrospectively. Results: Extracted PMMs with 2PR possessed the following distinguishing morphological traits: crown wider on the palatal half (55.3%), double Carabelli cusps (23.7%), pronounced palatal indentation of the crown (20.5%), thick palatal enamel extension (16.3%), palato-radicular groove (11.6%) and palatal enamel pearl (2.3%). Differences between second and third PMMs were not statistically significant (P > .05). At least one distinguishing trait was present on 63.4% and 94.1% of extracted and clinically evaluated PMMs with 2PR, respectively. Omega-shaped deformation of the dental arch may be the first clinically observable clue to this root constellation. Conclusions: Clinical examination of tooth morphology and shape of the dental arch is essential for the detection PMMs with 2PR. Background: To determine whether the presence of two palatal roots in permanent maxillary molars (PMMs) could be predicted by observing dental morphological traits during the clinical examination. Materials and methods: A total of 18 second and 26 third PMMs with two palatal roots (2PR) were examined from the collection of extracted teeth. The reference sample of 44 extracted PMMs with one palatal root was selected such that pairs of morphologically matching PMMs with one and 2PR were formed. The external morphology of these tooth pairs was examined under a stereomicroscope and distinguishing traits were registered. The Fisher’s exact test was applied to examine differences between second and third PMMs. Additionally, the external morphology of 17 PMM with 2PR in 15 patients was analyzed retrospectively. Results: Extracted PMMs with 2PR possessed the following distinguishing morphological traits: crown wider on the palatal half (55.3%), double Carabelli cusps (23.7%), pronounced palatal indentation of the crown (20.5%), thick palatal enamel extension (16.3%), palato-radicular groove (11.6%) and palatal enamel pearl (2.3%). Differences between second and third PMMs were not statistically significant (P > .05). At least one distinguishing trait was present on 63.4% and 94.1% of extracted and clinically evaluated PMMs with 2PR, respectively. Omega-shaped deformation of the dental arch may be the first clinically observable clue to this root constellation. Conclusions: Clinical examination of tooth morphology and shape of the dental arch is essential for the detection PMMs with 2PR.