The composition of the caudal skeleton of teleosts (Actinopterygil: Osteichthyes)

Abstract

The diural caudal skeleton of teleostean actinopterygians develops phylogenetically and ontogenetically from a polyural skeleton. The reduction of the polyural anlage to f w r , three, two or fewer centra in thc adult caudal skeleton takes different pathways in different genera (e.g. compare Elops and Albula) and groups o f teleosts. As a result, ural centra are not homologous throughout the teleosts. By numbering the ural centra in a homocercal tail in polyural fashion, one can demonstrate these and the following differences. The ventral elements (hypurals) always occur in sequential series, whereas the dorsal elements (epurals and uroneurals) may alter like the ural centra. The number of epurals, five or four in fossil primitive teleosts, is reduced in other primitive and advanrrd teleosts, but the same epurals are not zlways lost. The number of uroneurals, seven in fossil teleosts, is reduced in living teleosts, but it has not been demonstrated that the first uroneural is always derived from the neural arch of the same ural centrum. The landmark in the homoccrcal tail is the preural centrum 1 which can be identified by (1) bifurcation of the caudal artery and vein in its ventral element, the parhypural, (2) its position directly caudal to the preural centrum (PU2) which supports the lowermost principal caudal ray with its haemal spine, (3) carrying the third hypaxial element ventral to the course of arteria and vena pinnalis, and (4) by carrying the first haemal spine (parhypural) below the dorsal end of the ventral cartilage plate. The study of the drvelopment of the vertebral column reveals that teleosts have different patterns of centrum formation. A vertebral centrum is a complete or partial ring of mineralized, cartilaginous or bony material surrounding at least the lateral sides of the notochord. A vertebral centrum may be formed by arcocentrum alone, or arcocentral arcualia and chordacentrum, or arco-, chorda-and autocentrum, or arcocentral arcualia and autocentrum. This preliminary research demonstrates that a detailed ontogenetic .interpretation of the vertebral centra and of the caudal skeleton of different teleosts may be useful tools for further interpretations of teleostean interrelationships.

Dynamic skeletogenesis in fishes: Insight of exercise training on developmental plasticity

“…Nomenclature terminology for median fins follows that of Schultze and Arratia (1989), Arratia and Schultze (1992), Arratia et al (2001), Grü nbaum and Cloutier (2010), and Cloutier et al (2010). Figure 1 …”

The macrosemiiform fish companion of the Late Jurassic theropod Juravenator from Schamhaupten, Bavaria, Germany

“…The division between preural and ural regions is unclear so that we are unable to agree or disagree with the identification of the first hypural and of preural centrum 5 in Enchelyolepis and prefer to identify them with question marks in Figure 10. At least six hypurals are preserved in Voelklichthys, any of which is associated to a ventral chordacentra, a situation also present in lepisosteids (Schultze & Arratia 1986, 1989Grande 2010). It is expected that many more hypurals were present in Voelklichthys.…”

“…To avoid possible confusion of names with those of the traditional terminology, those of the traditional terminology are presented in parentheses the first time that the name is cited and also in the illustrations. Names of vertebral elements follow Schultze & Arratia (1989); Arratia (1997); Arratia et al (2001). Names and abbreviations used in the identification of different fin rays are those in Arratia (2008).…”

A new Late Jurassic halecomorph fish from the marine Vaca Muerta Formation, Argentina, southwestern Gondwana

“…Caudal endoskeletal terminology and caudal skeleton types follow Nybelin (1963Nybelin ( , 1971Nybelin ( , 1977, Arratia and Schultze (1992), and Schultze and Arratia (1986, 1989, 2013. The interpretation of caudal fin ray and associated elements follows Arratia (2008aArratia ( , 2009.…”

“…The interpretation of caudal fin ray and associated elements follows Arratia (2008aArratia ( , 2009. Vertebral centra terminology follows Schultze and Arratia (1986, 1989, 2013 and Arratia et al (2001). Scale terminology follows Schultze (1966Schultze ( , 1996Schultze ( , 2016.…”