Notes upon the intercostal arteries in some snakes by L.D. Brongersma Rijksmuseum van Natuurlijke Historie, Leiden From its the aortic arch which as a vessel, origin, right passes anteriorly, 3. Bifurcating arteries, arise single and the this of but which divide the branch obliquely to right; in part its course into two branches, one the the other the it gives off the two carotid arteries, or as the case entering the parietes to right, to be in of the vertebral column. may (e.g., Uropeltis melanogaster (GRAY)) left the common carotid trunk. It then curves dorsally, and the end of the dorsal 4. which arise medially, caudally. At curve, Longitudinally branching arteries, as a the arch the vertebral but which off branches which right aortic gives off artery, single vessel, give which close to the ventral surface of and the ramifications of runs cranially, pass cranially or caudally, the vertebral column, to enter the parietes at a great- which enter the parietes in the median line. er or smaller distance behind the head. In its further the aortic arch fuses with the left aortic which dis- course, right 5. Anastomosing arteries, arise at some arch to form the dorsal which tance from each other and which aorta, passes caudally as single vessels, close to the ventral surface of the vertebral column. divide into a cranial and a caudal branch; the The intercostal from the vertebral branch the connected arteries arise artery, caudal of one artery is to from the right aortic arch (between the origin of the the cranial branch of the next artery, and thus a vertebral artery and the fusion of the two aortic longitudinal vessel is formed parallel to the vessel and dorsal intercostal which off the arches), from the aorta. These (vertebral artery, aorta) gives arteries. and the this arteries pass dorsally, they enter parietes in From longitudinal artery, paired arteries arise, has been described BEDDARD and into the to the and left of varying ways, as by pass parietes right (1903; 1904a, b; 1906a, b; 1908; 1909) in a series of the vertebrae. of snakes. papers on the anatomy This author has pointed to the possible taxonomic value of the differ- 6. Paired arteries, which arise side by side from the the ences shown by the various genera and species, which vertebral artery or from the aorta, and one of he examined. However, before definite conclusions which enters the parietes to the right, the other be it will be examine the left of the vertebral column. can drawn, necessary to more to and the intercostal genera species. Studying arteries intercostal arteries of snakes is time-consuming; their number may be In some species the number of 156 in a of the number of vertebrae, in others the very high (e.g., specimen Xenopeltis uni- corresponds to color and has to be to two vertebrae. Reinw.), every artery checked, interspaces are equal or more because of intercostal arteries various types may oc- cur in one individual. The of intercostal be the intercostal of small following types arteries can In present notes the arteries a distinguished. number of species from various families are described to add data to those published by Beddard. It is 1. Single arteries, which enter the parietes in the hoped that further notes will be published in the median line. future, and that in it will become this way possible 2. Single arteries, which enter the parietes either to to evaluate the taxonomie importance of the diversity the right or to the left of the vertebral column. shown by these arteries in snakes. Downloaded from Brill.com10/01/2021 08:58:55PM via free access 54 L. D. BRONGERSMA costals and TYPHLOPIDAE are single again, alternating on the right left; the intervals are equal to the length of three or diardii mülleri Schl. Typhlops four vertebrae. This species shows three types of intercostal arteries, ANILIIDAE above. viz., the types 2, 3 and 6 mentioned The first two intercostals to arise from the vertebral Anilius scytale (L.) of the bifurcate of these Beddard described the intercostals artery are type (3); cranially (1906, pp. 33, 34) the of the less of this as all of the but majority arteries are single (2), more or species being bifurcating type, to the in the examined I bifurcate regularly, alternatin,gly going to the right or specimens by me, found left vertebra. and All intercostals of a Occasionally a bifurcating artery (3), paired (6), single (2) arteries. between the are intervals of one vertebra occurs single ones. regularly interspaced at arise from the short each. But two intercostals very right the first the second All intercostals from the vertebral aortic arch; is bifurcate, is sin- arising artery are gle (2). The series of intercostals arising from the of the bifurcating type. From the right aortic arch dorsal aorta can be divided into five parts. In the six bifurcating arteries arise. The majority of the first part of this series, the intercostals are single, intercostals given off by the dorsal aorta are of the the and each but down the liver regularly alternating on right left; one to bifurcating type, halfway a series vertebra. The second part of the series (at the level of paired intercostals is found. of the caudal half of the liver) is formed by bifurcate arteries (3), arising at interspaces of two vertebrae Cylindrophis rufus (Laur.) (Fig. 1) with of but occa- The intercostals each (rarely an interspace one vertebra); arise at regular intervals, one to few sionally a single arteries or paired arteries occur vertebra. The first two intercostals given off by the between the bifurcate vessels. The third part of the series (caudally of the liver) consists of single arteries, regularly alternating, and arising at interspaces of one vertebra. More caudally, the fourth part of the series is formed by bifurcating arteries, whilst the fifth part of again consists single, alternating arteries (with an occasional bifurcating artery intercalated between the single ones). All intervals of single arteries arise at one vertebra; the bifurcating arteries show interspaces of two verte- follow brae, except where they or precede a single from which but artery, they are separated by one vertebra. LEPTOTYPHLOPIDAE Leptotyphlops dulcis (Bd. & Gir.) Only one specimen was available, and I did not suc- ceed in checking the intercostals arising from the vertebral artery. Two intercostals arise from the right aortic arch; the first is of these single (2), and it enters the pa- the of the second intercostal rietes to right a vertebra; bifurcates before entering the parietes. The series of intercostals arising from the dorsal be divided into three The first of aorta can parts. of the these parts consists single arteries entering the of parietes to the right or to left the vertebral column; the interspaces are irregular in length. At Fig. 1. Cylindrophis rufus (Laur.). A.d., right aortic arch; the level of the the intercostals bifurcate be- kidneys, A.do., dorsal aorta; A.s., left aortic arch; A.v.vertebral fore entering the parietes. More caudally, the inter- artery. Downloaded from Brill.com10/01/2021 08:58:55PM via free access INTERCOSTAL ARTERIES IN SNAKES 55 Fig. 2. Uropeltis melanogaster (Gray); A.d., right aortic arch; A.do., dorsal aorta; A.m., artery ramifying in mesentery; A.r.d., right renal artery; A.r.s, left renal artery; A.s., left aortic arch; A.s.d., right spermatic artery; A.s.s., left vertebral cloaca;Downloaded from Brill.com10/01/2021 08:58:55PM spermatic artery; A.v., artery; A.v.d.; artery to vas deferens; c. arteries to r., arteries to rectum. via free access 56 L. D. BRONGERSMA vertebral off the artery, the eight given by right aor- from dorsal tic arch, and all those arising the aorta bifurcate before they enter the parietes. The third intercostal arising from the vertebral artery, and all those of the cranially it, are single, entering parietes in the median line (type 1). Anomochilus weberi (Lidth) This examined detail. As far species was not in as could be ascertained, the intercostals arising from the right aortic arch, and those given off by the dorsal intervals of vertebra aorta are regularly spaced at one each; they bifurcate close to the vertebral column. UROPELTIDAE Uropeltis melanogaster (Gray) (Fig. 2) In this species four types of intercostals (1, 2, 3, 6) are present. The first three intercostals arising from the verte- bral the further fifteen artery are bifurcate; inter- costals given off by the vertebral artery are single, and they enter the parietes in the median line. The aortic arch off but right gives one, bifurcating artery. The majority of the intercostals arising from the dorsal aorta are single (2), regularly alternating on the right but intervals of or left, irregularly spaced at one or two vertebrae. Towards the caudal end of the series a few paired intercostals occur. Two of the intercostals give off ramifications to the viscera. The first of these (fig. 2, A.m.) ramifies in the mesentery, and it sends branches to the liver, and to the intestine. The second (fig. 2, A.s.d.) gives off the right spermatic artery. At the level of the right it consecutive kidney appears as if two intercostals, which the connected pass to right parietes, are by a very narrow longitudinal vessel; the same applies to two intercostals, which go to the left parietes, but that I must point out I am not absolutely certain whether this observation and have is correct, I no other suitable specimen to check it. The distributionof the intercostals from which they arise, is indicated in fig.