On the ontogeny and orientation of the Triassic Conodont P1-element in Pseudofurnishius murcianus Van den Boogaard, 1966

Abstract

Successive growth stages of P1-elements in the Middle to early Late Triassic species Pseudofurnishius murcianus allows the observation of a detailed ontogeny. Besides the gradual enlargement of its curved blade and the growing number of its denticles, a small internal platform develops, eventually followed by an external one, both bearing denticles. The number of denticles on the blade and internal platform increases from five and one in the smallest specimens, respectively, to 14 and 9 in fully developed ones, whereby the distribution pattern of platform-denticles, on the inner one in particular, is of great morphological variety. For the orientation of the P1-element of P. murcianus, the comparison of the early development stages of Pseudofurnishius and Sephardiella, that share a common ancestry, permits to adhere to the orientation used by Diebel rather than to the one proposed by Van den Boogaard.

Résumé

La succession de stades de croissance d’éléments P1 de l’espèce du Trias moyen à supérieur Pseudofurnishius murcianus permet d’en observer l’ontogenèse complète. À part la dimension croissante de la lame et du nombre de ses denticules, une petite plateforme, elle aussi couverte de denticules, se développe sur le bord interne de la lame, parfois suivie plus tard d’une plateforme du bord externe. À mesure qu’elles grandissent, lame et plateforme interne voient le nombre de leurs denticules respectifs passer de 5 et 1 pour les spécimens les plus petits à 14 et 9 pour les spécimens au développement complet. La distribution de ces denticules présente en outre une grande variété morphologique, en particulier sur la plateforme interne. Pour l’orientation de l’élément P1 de P. murcianus, la comparaison des stades précoces des genres Pseudofurnishius et Sephardiella, qui ont une origine commune, nous porte à adhérer à l’orientation proposée par Diebel plutôt qu’à celle avancée par Van den Boogaard.

Introduction

Pseudofurnishius murcianus Van den Boogaard is a very distinctive Triassic conodont species, found in “Post-Carboniferous” strata in the Province of Murcia (Spain). This form, being identical with the Spathognathodus sp. of Diebel (1956), allegedly from the Cretaceous of the Mungo River in Cameroon, has a very particular small inner platform, unknown in the Palaeozoic genus Spathognathodus. The tendency to develop a platform led Van den Boogaard (1966) to establish the genus Pseudofurnishius for his new species P. murcianus, the P1-elements of which consist of a discrete compact curved structure with denticles and a small inner platform.

The alleged Cretaceous origin of Diebel's (1956) material was the result of mislabelling, as Förster and Weddige (1979) revealed, and originally from the Protrachyceras villanovae level of the Ladinian (Middle Triassic) at Mora-Camposines (Catalonia). Also, not knowing Boogaard's paper, Nogami (1968) followed Diebel's (1956) identification for the specimen that he found in the Triassic of Malaysia but did not illustrate, a finding of P. murcianus now ascertained (Hirsch et al., 2007, Ishida and Hirsch, in press). It was not before Huddle (1970) and Hirsch (1972) that P. murcianus was duly recognized as Ladinian. The discovery in Sinai and Palestine of the very first Triassic conodonts, P. murcianus among others, had no illustrations (Eicher, 1946, Eicher, 1947). Eicher and Mosher (1974) published these until then not illustrated specimens from Sinai and Palestine (Eicher op. cit.).

P. murcianus characterises the Sephardic Province (Hirsch, 1972, Hirsch, 1977), substantiated by occurrences in Spain (Van den Boogaard and Simon, 1973, Besems and Simon, 1982, Besems, 1983, March Benlloch, 1986, March Benlloch, 1991, Márquez-Aliaga et al., 1996, Plasencia, 2009), in Egypt and Israel (Eicher and Mosher, 1974, Huddle, 1970), Tunisia (Rakus, 1981) and Jordan (Bandel and Waksmundzki, 1985). It further occurs in the Late Ladinian and Lower Carnian of Italy (Catalano et al., 1990, Gullo and Kozur, 1991, Mastandrea et al., 1998, Balini et al., 2000, Jadoul et al., 2002), Slovenia (Ramovs, 1977, Ramovs, 1978, Krivic and Stajanovic, 1978, Kolar-Jurkovsek, 1990), Hungary (Kozur, 1993), Serbia (Budurov and Pantic, 1973), Turkey (Nicora, 1981) and Malaysia (Nogami, 1968, Hirsch et al., 2007, Ishida and Hirsch, in press).

To the palaeobiology of P. murcianus, Ramovs, 1977, Ramovs, 1978 contributed with his very well preserved clusters of P. murcianus that provided clues for the reconstruction of the conodont apparatus. Using a large population of more than 1,150 specimens, Bandel and Waksmundzki (1985) revealed aspects of the morphological variability of the species. Gullo and Kozur (1991) proposed a phylogeny of the genus Pseudofurnishius that included several species and subspecies of P. murcianus. Based on a large material from Spain, Plasencia et al. (2007) and Plasencia (2009) proposed improvements in the reconstruction of the P. murcianus apparatus.

Ontogeny remaining largely ignored in the literature, a complete description of its ontogenetic development is the aim of the present work.