CHAPTER XIII. 



THE MICROSAURIAN FAMILY HYLONOMID/C, FROM THE COAL MEASURES OF 



NOVA SCOTIA. 



Family HYLONOMIDiE Fritsch, 1883. 



Fkitsch, Fauna der GaFkohlc und dcr Kalksteine dcr Perm formations Bohmens, Bd. I, p. 159, 1883. 

 LvDEKKCR, Cat. Fossil Rcptilia and Amphibia, iv, p. 201, 1890. 



The following characterizations of the family are those given by Lydekker (393, 

 p. 201) based on Fritsch (251): Body slender and lizard -like; skull narrow, with 

 smooth or faintly sculptured bones; neural spines of vertebra; well developed, and 

 long, slender ribs. Teeth smooth, or with grooved summits. The whole body 

 covered with sculptured scutes. Internal gills may be developed. 



Fritsch (251, Bd. I, p. 159) gives the following in his original description: 



"Stegocephali von Baue schlanker Eidechsen mit schlanken langen Rippen. Wirbel 

 amphicoel mit stark entwickelten oberen Domfortsatzen. Schadelknochen glatt oder 

 schwach verziert. Schuppen gross, verziert, den ganzen Korper deckend. Zahne glatt oder 

 mit verzierte Spitze. Kiemenbogen bei einigen angedeutet. Mittlere Kehlbrustplatte 

 unbekannt. Coracoidea ahnlich wie bei Branchiosaurus schlank, winkelig gebogen." 



Fritsch includes the following genera in the family : 



Hylonomus, Hyloplesion, Smilerpeton, Seeleya, OrthoQosta, and Ricnodon. The family includes 

 the following species: 



Hylonomus lyelli Dawson, Nova Scotia. Hylonomus wildi Woodward, England. 



latidens Dawson, Nova Scotia. Smilerpeton aciedentatum Dawson, Nova Scotia. 



multidens Dawson, Nova Scotia. Hylerpeton dawsonii Owen, Nova Scotia. 

 wymani Dawson, Nova Scotia. intermedium Dawson, Nova Scotia. 



fritschii Gein. and Deichm., Saxony. longidentatum Dawson, Nova Scotia. 



geinitzi Credner, Saxony. Fritschia curtidentata Dawson, Nova Scotia. 

 (?) pictus Fritsch, Bohemia. 



Genus HYLONOMUS Dawson. 



Dawson, Quart. Jour. Geol. See. Ix)ndon, xvi, p. 274, figs. 14-18, 1860. 



Dawson, Air-breathers of the Coal Period, p. 44, 1863. 



Dawson, Phil. Trans. Roy. Soc. Ix)ndon, 1882, pt. 11, p. 634. 



Credner, Zeit. d. deutsch. geoL GescU., 1890 (i.\ Thcil, die Stegocephalen und Saurier). 



Type: Hylonomus lyelli Dawson. 



The genus Hylonomus is a very important one from a taxonomic viewpoint, 

 since it was regarded by Dawson (216, p. 635) as the typical genus of the order Micro- 

 sauria, the most abundant group in the Carboniferous. Unfortunately the species 

 of the genus Hylonomus are known only from fragmentary remains. I have re- 

 produced in plate 9 Dawson's figures of the remains of Hylonomus as published by 

 him in 1891. 



Dawson (216) gave, in 1882, the following definition of the genus Hylonomus: 

 "Form lizard-like, with the posterior limbs somewhat large in proportion to the 

 anterior. Size, small. Mandibular and maxillary teeth numerous, small, conical, 

 pointed. Palatal teeth minute. Abdominal scales oval. " 



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