https://repository.kopri.re.kr/handle/201206/14827 Wed, 08 Apr 2026 07:57:00 GMT 2026-04-08T07:57:00Z https://repository.kopri.re.kr/handle/201206/15085 Title: A giant stem-group chaetognath Authors: Park, Tae-Yoon S.; Morten Lunde Nielsen; Luke A. Parry; Martin Vinther Sørensen; Lee, Mirinae; Kim, Ji-Hoon; 안인혜; Park, Changkun; Giacinto de Vivo; M. Paul Smith; David A. T. Harper; Arne T. Nielsen; Jakob Vinther Abstract: Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstatte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to the Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, either as a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today Mon, 01 Jan 2024 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/15085 2024-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16219 Title: Periostracum in Cambrian helcionelloid and rostroconch molluscs: comparison to modern taxa Authors: Oh, Yeongju; John S. Peel; Yong Yi Zhen; Patrick M. Smith; Lee, Mirinae; Park, Tae-Yoon S. Abstract: The periostracum, a non-calcified organic layer that envelops the mineralized shell layer (‘ostracum’) of molluscs, acts as an initial framework for the calcified ‘ostracum.’ Despite its significance in biomineralization in molluscs, fossil examples of the periostracum are limited in the geological record, especially from the Palaeozoic era, due to its susceptibility to post-mortem decay. In this study, we describe radial threads found on the outer surface of Cambrian molluscs, including helcionelloids and rostroconchs, which we interpret as fossilized periostracal structures. These radial threads are observed in 13 species from five valid genera, exhibiting a widespread palaeogeographical distribution encompassing Gondwana (Australia), Siberia, western Laurentia (Utah), and eastern Laurentia (Greenland), and spanning Cambrian Stage 4？Drumian deposits. These radial threads always cover the outermost surface of shells, dividing it into regular intervals, and develop through incremental growth. They originate from the apical area of helcionelloids or the umbo of rostroconchs. Detailed examination has revealed that the radial threads initiate at the apical region, but may be absent from the protoconch (embryonic shell). The radial threads are most likely preserved by mineral encrustation on the periostracum. Similar, but not homologous, radial threads are found in other fossil and modern molluscan taxa, such as the adhesive radial lines of anomalodesmatan bivalves or the periostracal ridges of viviparid gastropods. Mon, 01 Jan 2024 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16219 2024-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/14901 Title: Cambrian lobopodians shed light on the origin of the tardigrade body plan Authors: Kim, Ji-Hoon; Smith F.W.; Kim, Sanghee; Rho H.S.; Zhang X.; Liu J.; Park, Tae-Yoon S. Abstract: Phylum Tardigrada (water bears), well known for their cryptobiosis, includes small invertebrates with four paired limbs and is divided into two classes: Eutardigrada and Heterotardigrada. The evolutionary origin of Tardigrada is known to lie within the lobopodians, which are extinct soft-bodied worms with lobopodous limbs mostly discovered at sites of exceptionally well-preserved fossils. Contrary to their closest relatives, onychophorans and euarthropods, the origin of morphological characters of tardigrades remains unclear, and detailed comparison with the lobopodians has not been well explored. Here, we present detailed morphological comparison between tardigrades and Cambrian lobopodians, with a phylogenetic analysis encompassing most of the lobopodians and three panarthropod phyla. The results indicate that the ancestral tardigrades likely had a Cambrian lobopodian-like morphology and shared most recent ancestry with the luolishaniids. Internal relationships within Tardigrada indicate that the ancestral tardigrade had a vermiform body shape without segmental plates, but possessed cuticular structures surrounding the mouth opening, and lobopodous legs terminating with claws, but without digits. This finding is in contrast to the long-standing stygarctid-like ancestor hypothesis. The highly compact and miniaturized body plan of tardigrades evolved after the tardigrade lineage diverged from an ancient shared ancestor with the luolishaniids. Sun, 01 Jan 2023 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/14901 2023-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/14948 Title: Homology of the head sensory structures between Heterotardigrada and Eutardigrada supported in a new species of water bears (Ramazzottidae: Ramazzottius) Authors: Kim, Ji-Hoon; Krzysztof Zawierucha; 노현수; Park, Tae-Yoon S. Abstract: Phylum Tardigrada is represented by microscopic eight-legged panarthropods that inhabit both terrestrial and marine environments. Although tardigrades are emerging model animals for the research including physiology, evolutionary biology and astrobiology, knowledge of their external morphology is still insufficient. For instance, the homologies between marine and terrestrial relatives largely remain unexplored. In this study we provide detailed pictures of the head sensory organs present in a new tardigrade, Ramazzottius groenlandensis sp. nov. The specimens were collected from a mixed moss and lichen sample on Ella Island, East Greenland. The new species differs from other congeneric species in having polygonal sculpturing on the dorsal cuticle, which is accentuated in the posterior region of the body, a lateral papilla on the leg IV, and distinctive egg morphology. A Bayesian phylogenetic analysis (18S rRNA + 28S rRNA + COI) confidently placed the new species within the genus Ramazzottius. Interestingly, the new species shows a full set of well-developed cephalic organs, which correspond to all sensory fields found in eutardigrades. Details on the full set of head organs were present only for heterotardigrades. The surface of these organs is covered with small pores, presumably playing a sensory role. This discovery suggests the homology of head sensory structures between heterotardigrades and eutardigrades, implying that the distinctive arrangement and positioning of sensory organs on the head was a plesiomorphic feature of tardigrades. Moreover, we found that the Ramazzottius oberhaeuseri morphotype forms a morphogroup, not a monophyletic species complex. Sun, 01 Jan 2023 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/14948 2023-01-01T00:00:00Z