“…The importance of apparatus architecture in suprageneric classification was also clearly shown by Donoghue (2001) and Sweet and Donoghue (2001). Lofgren (1990) demonstrated that many of the associated element types in platform-equipped ap paratuses like those discussed in the present publication had wart like extensions on the tip of the cusp, thus being readily distin guishable from the otherwise almost identical, homologous ele ments of Baltoniodus. Herein we describe in greater detail some of the elements that accompany the better known platform ele ments of Lenodus, Eoplacognathus and Yangtzeplacognathus.…”
Conodont elements other than those with platform ledges along the processes have often been unrecognized or disregarded in reconstructions and phylogenetic discussions of Ordovician “platform conodont genera.” The platform elements are larger than the other element types and often exhibit more rapid evolutionary changes in morphology. Nevertheless, to understand the evolution of, and relationships between and among “platform genera,” it is necessary to also consider the associated ramiform and geniculate elements. Thus, on the basis of large collections, together comprising 10,800 elements from Sweden and southern China, all element types of Lenodus antivariabilis (An, 1981), L. variabilis (Sergeeva, 1963), Yangtzeplacognathus crassus (Chen and Zhang, 1993) and Eoplacognathus pseudoplanus (Viira, 1974) are described and discussed. All these species had seven morphologically distinct element types, and probably seventeen individual elements in each apparatus. Ancestors and descendants of these species are discussed more briefly and it is concluded that the ramiform and geniculate elements also are characteristic within each lineage.
“…The importance of apparatus architecture in suprageneric classification was also clearly shown by Donoghue (2001) and Sweet and Donoghue (2001). Lofgren (1990) demonstrated that many of the associated element types in platform-equipped ap paratuses like those discussed in the present publication had wart like extensions on the tip of the cusp, thus being readily distin guishable from the otherwise almost identical, homologous ele ments of Baltoniodus. Herein we describe in greater detail some of the elements that accompany the better known platform ele ments of Lenodus, Eoplacognathus and Yangtzeplacognathus.…”
Conodont elements other than those with platform ledges along the processes have often been unrecognized or disregarded in reconstructions and phylogenetic discussions of Ordovician “platform conodont genera.” The platform elements are larger than the other element types and often exhibit more rapid evolutionary changes in morphology. Nevertheless, to understand the evolution of, and relationships between and among “platform genera,” it is necessary to also consider the associated ramiform and geniculate elements. Thus, on the basis of large collections, together comprising 10,800 elements from Sweden and southern China, all element types of Lenodus antivariabilis (An, 1981), L. variabilis (Sergeeva, 1963), Yangtzeplacognathus crassus (Chen and Zhang, 1993) and Eoplacognathus pseudoplanus (Viira, 1974) are described and discussed. All these species had seven morphologically distinct element types, and probably seventeen individual elements in each apparatus. Ancestors and descendants of these species are discussed more briefly and it is concluded that the ramiform and geniculate elements also are characteristic within each lineage.
“…varicostatus (Sweet and Bergström, 1962) and Spinodus spinatus (Hadding, 1913). The name-bearing species, Dzikodus tablepointensis (Stouge, 1984), is a characteristic species of the Darriwilian in Europe (Dzik, 1976; Löfgren, 1978, 1990, 2000b, 2004; Rasmussen, 1991, 2001), North America (Stouge, 1984; McCracken, 1991) , South China (An, 1987; Ding et al, 1993; Zhang, 1998a), Argentina (Ottone et al, 1999; Ortega et al, 2007; Feltes et al, 2013; Mestre and Heredia, 2013a), Tarim (Zhao et al, 2000; Zhen et al, 2011b) and New Zealand (Zhen et al, 2011a). An (1987) originally established the “ Polonodus ” tablepointensis Subzone with two subzones (the underlying “ Amorphognathus ” antivariabilis Subzone and the overlying Eoplacognathus suecicus Subzone) as subdivisions of the “ A .” variabilis –“ A .” antivariabilis Zone.…”
Section: Conodont Biostratigraphymentioning
confidence: 99%
“…Zhang (1998a) established Dzikodus to accommodate the Polonodus tablepointensis species group of Stouge (1984), the sinistral and dextral Pb elements of Dzikodus are unpaired and do not mutually form mirror images, unlike the situation in Polonodus . For Polonodus (inclusive of Dzikodus ), Löfgren (1990) proposed a seximembrate species apparatus, one geniculate (M), and three ramiform (Sa, Sb, and Sd) elements in association with the two platform (Pa and Pb) elements. Zhang (1998a) documented the different growth stages of the Pa elements of Dzikodus , and she indicated that secondary lateral processes will form gradually at the anterolateral and the anterior processes during the growth.…”
Forty-two conodont species belonging to 26 genera, which span the middle Darriwilian to the earliest Sandbian interval, are documented from the Wolonggang and Hatuke Creek sections in the Wuhai area of Inner Mongolia, North China. This conodont fauna is dominated by cosmopolitan and widespread species and accompanied by several endemic taxa. Four conodont zones, the Dzikodus tablepointensis, Eoplacognathus suecicus, Pygodus serra, and P. anserinus Zones, and three subzones, the Pygodus lunnensis, P. anitae, and Yangtzeplacognathus foliaceus Subzones, are recognized. Because of its slope habitat, the conodont fauna of Wuhai area differs from the coeval faunas on the North China Platform, which reflect a shallower and warmer water environment, but is similar to the contemporaneous faunas in Baltoscandia, South China, and Tarim. Moreover, the studied sections share several stratigraphically diagnostic taxa with the counterparts of the North China Platform and Western Newfoundland, which makes it an effective link for biostratigraphic correlations both regionally and internationally. The stratigraphically regular occurrences of Spinodus spinatus, a good index of a deep-water environment, represent a Spinodus biofacies that agrees with the Ordovician paleo-tectonic regimes of North China.
“…3E; Stouge 1984). The ‘falodiform’ M element, if correctly identified (Löfgren 1990; Zhang 1998), is quite underived. Some species of Polonodus show a conical appearance and very thin crowns of P elements, and the separate genus Dzikodus has been proposed for them (Zhang 1998; Mestre & Heredia 2013).…”
Section: Discussionmentioning
confidence: 99%
“…Figure 3Proposed homology of identified apparatus elements and their processes within the Distomodontidae (the remaining elements have not been found because of inadequate sampling, or are hard to distinguish from elements of neighbouring locations): (A) Distomodus staurognathoides (Walliser, 1964) (based mostly on Bischoff 1986); (B) D. pseudopesavis Bischoff, 1986; (C) D . kentuckyensis Branson & Branson, 1947 (after Rexroad & Nicoll 1971); (D) Moskalenkodus quinquiradiatus (Moskalenko, 1977 in Kanygin et al 1977); (E) Polonodus ( Dzikodus ) tablepointensis Stouge, 1984 (based on Stouge 1984; Löfgren 1990; Zhang 1998). …”
Section: Possible Ordovician Distomodontidsmentioning
Four kinds of robust elements have been recognised in Amorphognathus quinquiradiatus Moskalenko, 1977 (in Kanygin et al. 1977) from the early Late Ordovician of Siberia, indicating that at least 17 elements were present in the apparatus, one of them similar to the P1 element of the Early Silurian Distomodus. The new generic name Moskalenkodus is proposed for these conodonts with a pterospathodontid-like S series element morphology. This implies that the related Distomodus, Pterospathodus and Gamachignathus lineages had a long cryptic evolutionary history, probably ranging back to the early Ordovician, when they split from the lineage of Icriodella, having a duplicated M location in common. The balognathid Promissum, with a 19-element apparatus, may have shared ancestry with Icriodella in Ordovician high latitudes, with Sagittodontina, Lenodus, Trapezognathus and Phragmodus as possible connecting links. The pattern of the unbalanced contribution of Baltoniodus element types to samples suggests that duplication of M and P2 series elements may have been an early event in the evolution of balognathids. The proposed scenario implies a profound transformation of the mouth region in the evolution of conodonts. The probable original state was a chaetognath-like arrangement of coniform elements; all paired and of relatively uniform morphology. This was modified at the origin of protopanderodontids by the introduction of a medial S0 element, which resulted in the separation of the exposed unit of M and S series elements from the P series elements hidden in the throat. A rotation of the S series elements to an almost horizontal position in early prioniodontids may have promoted duplication of the M element pair. In Gamachignathus, Icriodella and Pterospathodus lineages, these elements are differentiated morphologically. Subsequent anteriorward bending of the P element series caused duplication of the balognathid P2 element pair, but they remained undifferentiated, even in the otherwise elaborate Promissum. The whole clade of conodonts with supernumerary element pairs in the apparatus has its roots in high latitudes of the Ordovician.
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