No. 10.] (10) 35

A New Lower Nothosauria froni Isihu near Y~znaizu, Mono•gun, Miyagi Prefecture.

By Hisakatsu YABE, and Tokio SHIKAMA. (Comm. by H. YAB'E,M.J:A., Dec. 13, 1948.) About ten years ago, K. Nagai'~ discovered reptilian bones in the Onagawa sandy slate exposed at a road-side cliff along the eastern slope of a lull, 96.2 m high, opposite Tyausuyamanear Isihu, Mon&gun, Miyagi Prefecture; the locality is at some 2 km youth of the small town Yanaizu and 15 km north of tai near the city Isinomaki. Inai is the type locality of the Hollarulites beds' in the Inai sandy slate; the latter is underlain by the Onagawa gray slate which rests on the Kbzima conglomerate and sandstone without break; these three members consti- tute the Inai series of Skyto-Anisic age, and is unconformable to the underlying Toyoma slate of Upper Permian age. The Onagawa gray slate differs from the Inai sandy slate, in being finer-grain- ed, sometimes calcareous and frequently more siliceous; sandstone layers are com- mo i in the latter, but la king in the former. The two formations are conform- able to each other, and the younger one has often ripple masks and rarely bone- fragments in its basal part. The reptilian bones found by Nagai near Isihu lie in the upper part (either upper Skytic or lower Anisic) of the Onagawa gray slate. The reptilian bones subsequently excavated by Nagai, Y. Inai and others, be- long to one rather well preserved individual, though the skull, cervical, most parts of fore- and aft-limbs and caudal region are missing. The slate with the skeleton, being traversed by numerous joints, could not removed as a single slab, but is broken into several fragments, large and small; its reconstruction was clone by Nagai in the laboratory of the Institute of Geology and Palaeontology, Tv hoku University, Sendai. The skeletal parts are not much dismembered; vertebral cehtra and neural spines are preserved in connection, but caudal vertebrae and, costae are shifted f or- ward, indicating burrial before considerable progress of decay and that the under- current of sea water mowed along the vertebral column. This saurian skeleton belongs, the writers believe, to the Nothosauria, because

1) K. Nagai : Geology of the Northern Side of the Oppagawa (in Japanese, MS). 2) C. Diener: Japanisehe Triasfaunen. Denksch. K. Akad. Wiss., Wien, mat.-nat. Kl., Bd. 92, 1915. 3) Y. Inai and T. Takahasi : Stratigraphical Study of the Southern Kitakarni Mountainland (in Japanese), Contribution from the Institute of Geology and Palaeontology, Tohoku Imp. Univ., iii Japanese Language, No. 34, 1940. (10)~6 H. YA$Eand T. SHIKAMA. [Vol. 24, the skeletaj parts thought to be c:lrpus are slel~derand not short polygonal as in usual in Iehthyosauria and , and to represent a hew type, for which the name lllctanotlt-osaur'usn'ippon,uvs, gn, et sp, nov, is given, rf1iS 1Sperhaps the first record of oriental Nothosauria Order Family Nopsea Genus Metanothosaur'us,gu. nov. Genotype: Metanothosaurus nipponicvs, sp. nor, Diagnosis (given on vertebrae and costae only) : Body 1.3 m long, thor~aco- lumber an(l sacral regions 0.54 m long. Vertebral column consisting of 26 tho- raco-lumber an(l 5 sacral vertebrae. Neural spine rather high. Costae long and slender. Near to Paranothosaurus. Geologicaloccurrence: `frisic, Holotype: Vertebral column of thoraco-lumber, sacral and caudal regions; costae, ventral costae, and parts of fore- and aft limbs. Characters : The skeleton embedded with its right side above is about 90 cm long antero•posteriorlyand 20-30 em wide, It consists of thoraco-lumber verte- brae, with costae, sacral and some caudal vertebrae; skull, cervicalvertebrae, most parts of caudal vertebrae, pectoral and pelvic girdles missing. The vertebral co- lumn has 22, vertebrae set closely to each other; beside, there are 4 isolated pop- tenor; in living state there were mole than 26 vertebrae in the thoraco-lumber to caudal regions. Neural spines are attached to the vertebrae Nos. 1-16; 2. of the detached vertebrae also bear neural spines. There are 24 right costae, No. 13 costs attaching to the No. l vertebra, and No. 24 Costato the No. 12 vertebra, Nos. 1 and 2 costae are short, but certainly much longer in original state. Assu- ming the No. l Costaas belonging to the first thoraco-lumber vertebra, the No. 1 vertebra is in the original condition the 13th; hence the vertebral column of the thoraco-lumber to caudal regions consistedof more than 38 vertebrae r urther, there is one more Costabehind the No, 24 Costa; it is counted as No. 25. As the No. 14 vertebra is quite similar in external aspect to the anterior ones and some- what dtherent from the next posterior one; it is thought to be the last one of the thoraco-lumber vertebrae; thus the costae as well as the corresponding vertebrae' in the thoraco-lumber region are 26 in number. The assumed last vertebra of the thoraco-lumber region is followedposteriorly by 12 vertebrae; 5 of them, na- mely Nos. 15-19, are believed to be sa oral,being very similar to each other in general aspect; and h:.ving, rear the Nos. 18 and 19 vertebrae, 3 bones thought No., 10,] A New Lower Triassic Nothosauria from Isi hu near Yanaizu. (10), 37

to be sacral costae. On the above assumption, the writers consider the present vertebral column to consist of 26 thoraco•lumber-, 5 sacral- and more than 7 caudal vertebrae. The thoraco-lumber and sacral regionstaken together is about 54 cm long; the cervical and caudal regions restored, the vertebral column in the original state m }y have attained some 1.3 m in length. The dimensions measured of eaci vertebra are given below (m mm). (10) 38 H. YABE and T. SHIKAMA. [Vol. 24,

The thoraco-lumber vertebrae has a general tendency to become larger pos- teriorly; as to the centrum, it is ]ongest in the Nos, 9-11 vertebrae and highest in the Nos. 16-20, while the neural spine is highest in the No. 16 vertebra. In lateral aspect, the centrum is short, higher than long, apparently amphicoelous aid more concave in the posterior side than in the anterior. Both the posterior and anterior sides bend backward, and the postero-ventralangle is distiuctly pro- jected backward. Fossa of moderate size at a little higher than the middle of the centrum is probably the face for the articulation of Costa. Pre- and postzygapo- physes are well developed. Neural spine is relatively high and bends backward; the upper border is quite straight. The neural spines of the Nos. 7-15 vertebrae are not +rc'iipresrved in their basal part; they are also poorly preserved in the vertebrae posterior to the No. 17 vertebra, Neural arch is more than 10 mm high. The dimensions o£ the costae are given below (right costae in the upper line and the lower costae in the lower) : No. 10.] A New Lower Triassic Nothosauria from lshihu near Yanaiau. (10) 39

There are 24 or 25 right costae in successiona& stated above; the distal part is well preserved in the Nos. 3--6 costae and lost in the others, and possesses straight borders. The proximal part is also lacking in most of the costae; where preserved, it is apparently double-headed. All the costae curve strongly in their somewhat twisted proximal part, but gently elsewhere. The distal parts of 2 left costae occur between the No. 10 and 12 right costae; Nos. 19, 20, 21, 23 and probably 25 left costae are also preserved at the positions near the respective `right costae. Four left costaeat the dorsal side of the vertebral column are Nos. 15-18; of them Nos 16 and 18 are best preserved, the former being about 22 mm long along the anterior border and the longest and perhaps the most complete one of all the costae in thus skeleton. Of sacral costae, there are preserved proximal portions of 3 right ones, which are nearly straight and expanded at proximal end; further, a sacral Costaprobably of the left side occurscrossing the No. 18 left costs, and is likewise straight and expanded proximaly. More than 120 ventral costae are preserved; all of them are shifted forward as already stated at the outset, lying anterior to the No. 14 Costain random direc Lions; accordingly it is uncertain whether or not the numbers of the gastra1ia series are 3 (as in Kokon and Meyer's interpretation of Nothosat rvs), 4 (as in Kunisch's interpretation of Notliosaurus) or 5 (as in Paranothoscurus or Pachy- p1eurosaurns). The ventral are slender and thin, the longest one measuring 70 mm. Fore. and aft limbs: Humerus, radius, ulna and large parts of phalanxes are unknown. Probable radiale and ulnale occur anterior to the No, l Costa; the radiate is subqundrate, about 18 mm long and 12 mm wide, while the ulnale is quadrate and 8 x 6 mm in size. Among fragments of some probable left cos- tae and ventral costae in the anterior part of this specimen, there are found 7 phalanges, which are generally short and slender, expanded distally avid proxi- mally; the largest one is about 18 mm• long. Of hind limb, 1 probable tibia (10) 40 H. YABE and T. SHIKAMA. [Vol. 24, and 2 metatarsi are preserved, the former lies posterior to the neural spine of the No. 16 vertebra, and the latter posterior to the Nos. 19 and 20 vertebrae- Tibia is slender, thin and short, with proximal and distal expansion; it is about 50 mm long and 16 mm wide at the distal end. The probable 5th metatarsas lying be, hind the No. 20 vertebra is about 20 mm long and 13 mm wide at the proxi- mal end. Considerations: Owing to the lack of important osteological data, it is very difficult to deter- mine proper taxonomic position of the present species amongg the Nothosauria. It should be born in mind that the early taxonomic and osteological knowledge of thus group of reptilia is fragmental and is still so regardless of the good specimens later discovered from the Triassic of the " Tessiner Kalkalpen " and numerous nothosaurian remains discovered from various places in middle Europe since 1883,thus the presentwriters are oblige to take stepsfor provisionallyfixing. the approximate taxonomic position of the present fossil, which is the first notho- sauria from the Far East. Nothosaurias are hitherto known mostly from the Muschelkalk of South , and North ; t outside Europe, they are very rare, being recorded only from the Triassic of the Dead Sea region, Trans,Jordania and the Alcove limestone of Wyoming, U.S.A. As shown by the important works of B. Peyer, the skulls are less significant than the vertebral colum for the classification of Nothosauria.~ E, von Nopsca and Peyer classified them into two families, Pachypleurosauridae anc Nothosauridae.`~ The former comprises Pachypleu- rosaurus, Anal osaurus, Neusticoshurus, , Proneusticosawrw$,Phy- gosaurus and severalothers, and the latter Nohosaur s, Germanosaurus, Cyma- tosaurus, Postsaurus, Paranothosaurus (Nothosaurinae Nopsca), , Macromerosausus, , Rheticonia and other (Lariosaurinae Nopsea). Peyer states that, in the Pachypleurosauridae,sacral vertebrae are 3 or 4 in num- ber, sacral costae are set close to each other, and the median carpus is small, while in the Nothosauridae, sacral vertebrae are 5 in number, sacral costae are separate from each other, and the median carpus is large. Pachypleurosaurus is rather

4) B. Peyer : Die Triasfauna der Tessiner Kalkalpen, XIV. Paranothosaurus amsicri, nov. gen., nov. sp. Abb. Schweiz. Pal. Geseli., Bd. LXII, 1939. 5) H. Schroeder : Wirbeltiere tier nidersdorfer Trias, 1. Die Gattung Notiiosaurus in unteren Muschelkalk. Abh. Preuss. Ceol. Landesanst., n.f., Ht. 65, 1914. G. Corroy : Lcs vertebres du Trias de Lorraine et le Trias Lorraine. Ann. Pal., tom. 17, 1928. B. Peyer : op. cit., IV. Neubeschreibung tier Saurier von Perledo. -L.c., Bd. LIV, 1934. 6) B. Peyer, op. cit., 1939. 7) 0. Kuhn : Die fossilen Reptilien, 1937. B. Peper, op. cit., 1931. No. 10.] A New Lower Triassic Nothosauria from Isihu near Yanaizu. (10a 41 small in size, being about 40 cm in total length, and has usually low neural spines. Hence the saurian skeleton now at hand seems to belong to the Nothosauridae.

Paranothosaurn ansler-i Peyer is about 4 m in the total length, 50 cm in skull length and consists of 19 cervical-, 26 thoraco-lumber-, 5 sacral- and 60 caudal vertebrae; it carries rathef high neural spines, and is generally larger than Notho- saurus. The present Netanothosaurus seems to be included in the larger type with rather high neural spines as in Nothosaurinae, and not to the relatively smal- ler type with rather low neural spines as in Lariosaurinae; in the construction of vertebral column 111etanothosaurus is near Paramothosaurus, but is distinguished from it by having more slender castae, and being smaller in size. is almost representedby skulls only, very little being reported on its vertebral co- lumn; in N. ranbi Schroeder 1914, however, it is known that its vertebral co- lumn, about 27 cm long, bears 21 thoraco-lumber vertebrae. Metanothosaurus is distinct from Nothosaurus in this respect; the former is moreover characterized by its thin and slender costae, which the writers do not regard gasdue to the mode of preservation. At any rate, Metamothosawi~res seems to be a new nothosauria of the Nothosalrinae and related to Paranotliosa urns. Nothossauria appears first in the Anisic and is most common in the Middle Triassic; hence the probability is increased that the reptilian horizon of the Ona- gawa gray slate is rather Anisic than Skytic in age.