北九州市立自然史・歴史博物館研究報告A類(自然史)
Online ISSN : 2435-7545
Print ISSN : 1348-2653
3 巻
選択された号の論文の9件中1~9を表示しています
原著論文
Papers derived from the Symposium of Early Cretaceous Terrestrial Biota
  • Yoshitaka Yabumoto, Makoto Manabe
    2005 年 3 巻 p. 121
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー
  • Shinji Isaji, Hiroko Okazaki, Ren Hirayama, Hiroshige Matsuoka, Paul M ...
    原稿種別: 研究論文
    2005 年 3 巻 p. 123-133
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー

    The bone-bearing beds of the Lower Cretaceous Kuwajima Formation (Tetori Group) are described. Three facies of bone-bearing beds (Facies I: carbonaceous sandstones; Facies II: dark grey fine-grained silty sandstones; Facies III: dark greenish-grey mudstones) are present in inter-channel deposits that originated on a floodplain. The grain size of the sediments, and plant and molluscan fossils occurring in each bone-bearing bed, indicate that Facies I was deposited in a peat marsh, Facies II in a shallow lake, and Facies III in a vegetated swamp.

    Isolated small bones and teeth are the most abundant vertebrate fossils. Common elements in Facies II are aquatic vertebrates such as fishes and turtles. Facies III is characterized by the occurrence of terrestrial lizards, tritylodontid synapsids and mammals. Vertebrate fossil assemblages in Facies II and III are not mixed with each other even though they both represent parautochthonous assemblages. In contrast, Facies I is allochthonous, and is composed mostly of reworked sediments from Facies II.

    Depositional environments of the bone-bearing beds are strongly correlated with the composition of their fossil assemblages, indicating that different facies preserve the original faunal differences that existed between the shallow lake and vegetated swamp environments.

  • Yoshitaka Yabumoto
    原稿種別: 研究論文
    2005 年 3 巻 p. 135-143
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー

    Early Cretaceous freshwater fish fossils from the Kuwajima Formation of the Itoshiro Subgroup, Tetori Group described in detail for the first time are assigned to Lepidotes sp. (isolated scales), Sinamiidae (many isolated bones and scales), Pachycormidae (a dentary), Osteoglossiformes (a disarticulated skull with vertebrae and scales) and Teleostei (isolated scales).

  • Kyoichiro Ueda, Taewan Kim, Tateyu Aoki
    原稿種別: 研究論文
    2005 年 3 巻 p. 145-152
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー

    Early Cretaceous fossil dragonfly Hemeroscopus baissicus Pritykina was discovered from Korea. This is the first record of this species from this area and the description of wings is given.

  • Francisco José Poyato-Ariza
    原稿種別: 研究論文
    2005 年 3 巻 p. 153-168
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー

    The fishes from the Early Cretaceous (early Barremian) locality of Las Hoyas, in the Spanish province of Cuenca, are reviewed from a palaeoecological point of view. Las Hoyas was a permanent lake surrounded by actively interacting wetlands, with dry and humid cycles; no marine influence has been detected. A good number of the most generalized fishes from the lake, as well as small piscivore forms, would probably get into the wetlands in different extents throughout time, according to the availability of additional ecological space and food sources. Other fish taxa, such as the pycnodonts and the largest piscivores, must have had more physically restrained niches, probably somehow related with the humidity cycles in the palaeoenvironment. Juvenile fishes are largely represented in this locality, including events of mass mortality. The adults show a very interesting phenomenon of size reduction, probably related with environmental stress.

    The ecomorphologic overview of the fishes from the permanent waters of the Las Hoyas lake confirms that they must have occupied different niches, which, according to the lacustrine ecological spaces, can be grouped into:

    1) nekton related with the pleuston/plankton, such as the plankter Pleuropholis (Pholidophoriformes) or the surface insect-larvae eater Gordichthys (Chanidae), plus juvenile stages of many taxa, and possibly some other primitive teleosts that were plankton filters;

    2) nekton in strict sense, including the piscivore Caturus, Amiopsis, and Vidalamia (Amiidae); the water-bug eater Notagogus (Macrosemiidae); the shrimp-eater Lepidotes (Semionotidae), and ram feeder Rubiesichthys (Chanidae), plus a large amount of primitive teleosts, which constituted the major component of the Las Hoyas fish biomass;

    3) nekton related with the benthos, such as the predatory coelacanth cf. Holophagus and the pycnodonts Stenamara and Turbomesodon, adapted to a durophagous diet.

    A hypothesis of sexual dimorphism for the chanid teleost Rubiesichthys gregalis is proposed. Both morphotypes are discriminated by their relative body height only, and do not differ in any other morphometric, meristic, or anatomic character. They both occur in the same levels of the same localities, in about a 50-50% ratio for adult individuals, and there is no difference between the morphotypes and specimens from both known populations, El Montsec and Las Hoyas. Consequently, the two morphotypes of Rubiesichthys are interpreted as sexual dimorphs of a single species, R. gregalis. According to the variation found in Recent fishes, the higher-bodied morphotype is proposed to be the female dimorph, and the lower-bodied morphotype, the male dimorph. Differentiation of sexual dimorphs begins at about 20 mm; all specimens below that length show slender bodies only, and are considered juvenile.

  • Francisco José Poyato-Ariza
    原稿種別: 研究論文
    2005 年 3 巻 p. 169-184
    発行日: 2005/03/31
    公開日: 2021/03/10
    研究報告書・技術報告書 フリー

    Some examples of morphologic variation of body and fins morphology in Pycnodontiformes are shown; not all are butterfly fish-like, as the common place assumes. Pycnodonts are characterized by a heterodontous dentition; teeth on the vomer and the prearticulars are molariform, yet of diverse shapes, whereas teeth on the premaxilla and the dentary do exhibit even more diverse morphologies. This morphologic variation is also analyzed, and the inaccuracy of another common place, the "crushing" or "durophagous" dentition of the pycnodonts, is explained: these terms refer to function, not to form.

    The ecomorphologic evaluation of both sources of morphologic variation, body and dentition, indicate that pycnodonts may have been adapted to a large variety of potential diets and environments. The environment of pycnodont fishes is often believed to have been reefal, but this is not necessarily the case, since their adaptations are not exclusively functional in reefs or even in marine environments only. Examples of freshwater pycnodonts are mentioned, showing that these fishes are potentially misleading palaeoenvironmental indicators: their mere presence in any given locality is not an unambiguous indication of its palaeoenvironment.

    The ecomorphologic plasticity of pycnodonts was a key factor for their success as a group. This, together with a re-evaluation of their fossil record, leads to a new interpretation of the evolutionary history of the Pycnodontiformes.

feedback
Top