盾皮魚是一大類原始有甲魚類,。雖然完全滅絕，但它們神秘的解剖體系有可能含有關(guān)于有頜類脊椎動(dòng)物,、包括我們?nèi)祟愖约貉莼瘹v史的線索,。一個(gè)新的化石發(fā)現(xiàn)，澄清了關(guān)于Incisoscutum的生殖機(jī)制的問題,。
Incisoscutum作為節(jié)頸魚家族（一個(gè)大而重要的盾皮魚類別）的一個(gè)成員尤為研究人員所感興趣,。研究人員最近發(fā)現(xiàn)了一只成年Incisoscutum ritcchiei雌性個(gè)體的一個(gè)保存完好的化石，它含有胚胎,，這是體內(nèi)受精的證據(jù),。而新發(fā)現(xiàn)的化石是該物種的一個(gè)雄性個(gè)體，長(zhǎng)有陰莖一樣的交腳器,，與化石褶齒魚（一類未披甲的盾皮魚）和鯊魚中所見的相似,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 460, 888-889 (13 August 2009) | doi:10.1038/nature08176
Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires
Per Ahlberg1, Kate Trinajstic2,3,4, Zerina Johanson5 & John Long6,7,8
1 Subdepartment of Evolutionary Organismal Biology, Department of Physiology and Developmental Biology, Uppsala University, Norbyv?gen 18A, 752 36 Uppsala, Sweden
2 Western Australian Organic and Isotope Geochemistry Centre, Department of Applied Chemistry, Curtin University, Perth, Western Australia 6102, Australia
3 Earth and Planetary Sciences, Western Australian Museum, Perth, Western Australia 6000, Australia
4 School of Earth and Environment, The University of Western Australia, Perth, Western Australia 6009, Australia
5 Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
6 Museum Victoria, PO Box 666, Melbourne, Victoria 3001, Australia
7 Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 2600,
8 School of Geosciences, Monash University, Clayton, Victoria 3800, Australia
Recent finds1, 2 demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata)3, 4, making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be identical in males and females, with males presumed to have an additional cartilaginous element or series forming a clasper. Here we report the discovery of a completely ossified pelvic clasper in Incisoscutum ritchiei (WAM 03.3.28) which shows that this interpretation was incorrect: the basipterygium described previously1 is in fact unique to females. The male clasper is a slender rod attached to a square basal plate that articulates directly with the pelvis. It carries a small cap of dermal bone covered in denticles and small hooks that may be homologous with the much larger dermal component of the ptyctodont clasper.
