p. 19-26, [1] leaf of plates : ill. ; 24 cm.Includes bibliographical references

Case, E. C. (Ermine Cowles), b. 1871.

American Museum of Natural History Scientific Publications

56.8i, 7 E: 14-71, 5Article II. ON THE SKULL OF EDAPHOSAURUS POGONIASCOPE.By E. C. CASE.PLATE VII.The description of the skull of Edaphosaurus is a portion of alarger work on the Pelycosauria in course of preparation by theauthor. The work was carried on by aid of' a grant from the Car-negie Institution of Washington and is published in advance of thecompleted work by the permission of the Institution.The skull is the property of the American Museum of NaturalHistory, forming a part of the Cope Collection, and was placed at mydisposal for description by the Curator of Vertebrate Palaontology,Professor H. F. Osborn, to whom my thanks are due.Family JDAPHOSAURIDA Cope.Proc. Am. Phil. Soc., Vol. XX, I882, P. 450. Also Pal. Bull. 35.Proc. Am. Phil. Soc., Vol. XX, I883, p. 63I. Also Pal. Bull. 36.Type:-A nearly complete skull with the lower jaw of the left side and theimperfect axis. No. 4009, Am. Mus. Nat. Hist. Cope Coll. From Texas.In his Systematic Catalogue of the Vertebrates of the PermianFormations of North America, published in i888, Cope abandonedthis family, placing the genus in the family Clepsydropidae. It ishere restored for reasons that appear in the text below.Genus Edaphosaurus Cope.Proc. Am. Phil. Soc., Vol. XX, I882, P. 448. Also Pal. Bull. 35.Trans. Am. Phil. Soc., Vol. XVII, I892, pp., I5 1. xi, figs. 5 and 5a.Description of the Family and Genus: - Aberrant Pelycosaurs, littoral orestuarine in habit; feeding upon molluscs and crustaceans. Skull low, wideposteriorly, and tapering to the anterior end. A large superior temporal fora-men, and, probably, a smaller inferior one. Interparietal and epiotic present.Incisor teeth approaching chisel-shape; anterior maxillary teeth broadly tri-angular and thin with anterior and posterior cutting edges; posterior maxillaryteeth conical; posterior teeth of the lower jaw all conical. On the pterygoidand palatine and on the dentary large patches of stout crushing teeth.The specimen of Edaphosaurus pogonias Cope is unique, nothingidentifiable with it occurring in any other collection from the Per-mian of North America. The depressed form of the skull and theIg -20 Bulletin American Museum of Natural History. [Vol. XXII,suggestion of the axis that the vertebra were low and broad indicateaffinities with the Cotylosauria, but the temporal region with itsenormous superior temporal vacuity and almost certain inferiorvacuity as well indicates affinities with the Pely lgauia.As thecondition of the temporal arche-s it of more fundamental importancethan that of the shape, of the skull and the vertebrae, the animal isreferred tentatively to the Pelycosauria, family Edaphosauridze. Itshabits of life must have been very similar to those of Placodus andif future discoveries should show that it really possessed a singletemporal vacuity or that the inferior vacuity was decadent, thekinship of Edaphosaurus with Placodus as an ancestral form wouldbe strongly suggested.The skull is roundly triangular and flattened above; the temporalregion is elevated and the upper surface descends in an almost straightline to the anterior end./.Pl*x g.~The external nares arePI /??X. small and nearly terminalbut open laterally. The0-txvs> j, \ orbits are of moderate sizeN/gA,\, px \&and look nearly straightoutwards. The dentition/L,-.wW\:QX is very peculiar, varyingi/8Xoo°o%%O\ 'i from chisel-shaped incisors/Pr.If/ 8 ooo88toooo \t thin, triangular cutting*0o0 teeth in the anterior por-Fr, | g$000 tion of the maxillary andPoc.,0ooe oo X conical teeth in its poste-A0 0000I oj.-1 0 00 v , nor portion.K ~~~~~~Thepremax-illary isPa. Bs -, short and relatively broadBo. 0op /'but with a long posteriorPo,, prolongation in the medianSq^ line which extends back toFig. I. Fig. 2. join the nasals. There areFig. i.-Diagram of the upper surface of the skull ofEdafhosaur,us. x ,. P.mx. premaxillary, Na. nasal, Mx. max- four teeth in each premax-illary, L. lachrymal, Prf. prefrontal, _7u. jugal, Fr. frontal. Pof. illary which are badlypostfrontal, Po.o. postorbital, Pa. parietal, Ifi. interpaTietal, worn but wereSq. squamosal, Psq. prosquamosal, Qj. quadratojugal. x w apparentlyFig. 2. Lower surface of the same. P.v. prevomer; P.l. furnished with a strongpalatine; P.t. pterygoid; stf. stapes; Bo. basioccipital; Bs. t cuttingbasisphneoid: .,.oc. paroccipital. x t asomething like that of the modern rodents, or the ancient Placodus.The teeth projected slightly forward from the alveolar edge.1906.] Case, Skull of Edaphosaurus. 21The posterior edge of the bone forms the anterior edge of the nares.The maxillary is a broad plate extending upward somewhatobliquely and uniting with the nasals above and the premaxillaryanteriorly. The antenror cdge forms the posterior edge of the naresand the posterior end lies below the mici4ie of the eye socket. Thereare fourteen teeth in the bone; the anterior 1eare thin triangularo~~~~~~~~~~F. 0- SFig. 3.-Diagram of the lateral view of the skull of Edaphosaurus. Lettering the same as in figure i. x 2plates that originally had well developed arnterior and posteriorcutting edges but these have been largely destroyed by decay. Theposterior nine teeth are conical. All the teeth are in sockets andrest against the outer edge of the bone, which descends lower thanthe inner.The nasals are broad flat plates emtracing the premaxillariesanteriorly and extending between the frontals posteriorly.The frontals are very broad and flat; they meet the parietalsposteriorly in a wide suture and form the major portion of the upperedge of the orbit.The prefrontals form the upper anterior corner of the orbit.The lachrymals are short bones, rounded anteriorly and extendingback on the floor of the orbit to the anterior third of the lower edge.The parietals are flat anteriorly with a good-sized parietal foramenbut the posterior portion is somewhat convex. The bones of thetwo sides meet in a slight depression so that the crown of the skull isarched antero-posteriorly and depressed in the midline. The outeredge is concave and forms the upper border of the superior temporalvacuity. From the posterior outer corner a process curves gentlyoutward and downward to unite with the squamosal.The interparietal. Between the parietals posteriorly is a smalldiamond-shaped bone which extends downwards beyond the parietalsand separates the pair of bones below.The postfrontal is represented by a fragment of bone between theI90o6.] Case, Skull of Edaphosaurus. 21-22 Bulletin American Museum of Natural History. [Vol. XXII,frontal and parietal whose posterior edge forms the anterior edge ofthe superior temporal vacuity; the lower edge is missing.The postorbital and jugal are not distinct.The quadrate resembles that of the oher--Pelycosauria; the upper,portion is thin and plate-like and the lower end carries two largecondyles, the outer-e6inewhat more posterior than the inner. Thelong axis of the condyles is inclined somewhat inward. The outercondyle is extended backward as in Dimetrodon, forming a sort ofshelf on which rests the lower end of the quadratojugal.The quadratojugal and prosquamosal occupy the same relativepositions as in Dimetrodon. The first rests against the posterior edgeof the quadrate and overliesthe posterior edge of the pro-P.,p > squamosal. There are indi-EPa Sq. cations that a quadrate fora-men was present but it isXVwso. W s Sclosed inL the specimen, per-/l.. haps by pressure. SuperiorlyExc, P,CC. the quadratojugal passes be-\J__6t Q low the lower ends of the,Fig. 4,-Posterior view of the skull of Edahhosaurus. Let- squamosal and a second bone,tering the same as in figure i. Ex.o. exoccipital, ,So. supra- the epiotic (?) The anterioroccipital, E}o epiti .xoccipital,oSb.iot c. *'. end of the prosquamosal isbroken away, but it reaches up as far as the upper edge of the quad-rate touching the lower end of the squamosal.The squamosal is a thin and slender element, convex in curvature,which joins the parietal above and the quadratojugal and the pro-squamosal below. At itslower end a wide processstarted forward toward thepostorbital, but this is bro-ken so that its anterior con-nections cannot be madeout. The process evidentlyis a portion of a bridgeacross the temporal vacuity;Cope considered that therewas but one such bridge and Fig. 5.-Posterior view of the skull of Placodus. Afterthat the animal had a single v. Huenie. Lettering the same as in figure T.temporal arch, but the condition of the specimen makes probablethe presence of a second arch below.Epiotic (?).-This is the element referred to by Cope as "perhapsa transverse process of the supraoccipital." Below the parietal andinterparietal and above the posterior wall of the cranial cavity is apair of slender curved bones; lying next to the lower edge of thesquamosal they extend outward and downward until they touch theupper ends of the quadratojugal. These bones are in the exactposition of the epiotics and there is little doubt that they are homo-logous with the same bones in the Cotylosauria and Stegocephalia.They do not occur in the other families of the suborder. The nameepiotic was originally used for a different element ; it is here usedfor the element so called by Cope in Cotylosauria.The posterior surface of the cranium is formed by a single mass ofbone, the sutures between the basioccipital, supraoccipital, exoccipitals,and the paroccipitals are not distinguishable. The plate is partlyobscured in the specimen by the crushing which has forced theparietals with the interparietal and the epiotics down over it as faras the foramen magnum. The paroccipital processes extend out-ward nearly to the quadrate. The occipital condyle is relativelybroad and oval in outline, with no pit marking the position of theanterior end of the notochord.The basisphenoid has the same form as in Dimetrodon but is rela-tively longer. It has a strong parasphenoid process, well developedarticular faces for the pterygoids, and a large pit on the lowersurface.The stapes.-On either side of the basisphenoid is a short, widebone which occupies the position of a stapes. The inner end issmaller but terminates in a flat surface; just below the extremity thebone is pierced by a foramen.The palate is well preserved on one side. There is a great medianvacuity forming the posterior nares but there are no palatal vac-uities. The sutures between the pterygoids, palatines, and prevo-mers cannot be miade out.The prevomers are thin plates connecting anteriorly and laterallywith the premaxillaries and anteriorly with each other; more poste-riorly they are cut out on the median line so that when the two werein position there was an elongate heart-shaped vacuity in the medianline. At the anterior end where the two bones meet there are fourconical teeth on each bone; the posterior is the larger.The pterygoids articulate with the basisphenoid in the midline andsend a strong process backward which articulates with the inner sideof the lower end of the quadrate. There is no descending externalIi go6.] Case, Skull of Edaphosaurus. 2324 Bulletin American Museum of Natural History. [Vol. XXIIprocess forming a buttress for the lower jaw as in the otherPelycosauria. The line of union with the palatine cannot bemade out.Covering a large portion of the pterygoid and the palatine is anoval plate studded thickly with stumpy conical teeth irregularlyarranged. On the inner edge there are some teeth of smaller size.Most of the teeth are injured by decay but it can be seen that theends were very blunt, resembling the pharyngeal teeth of Labrus.The plate bearing the teeth is very heavy and extends backwardsunderlying the anterior half of the temporal region.The lower jaw of the left side is nearly perfectly preserved. Thesutures between the separate bones cannot be made out. The an-terior symphysis is very strong and was formed by the splenial aswell as the dentary. There are twenty counted teeth and alveoliand there were perhaps three or four more at the posterior end.The anterior teeth are similar to the premaxillary teeth above butthere are none corresponding to the triangular teeth of the anteriorportion of the maxillary; ail are conical, growing smaller toward theFIG. 6.-Lower jaw of EdaphlosauriLs. xa.posterior end. The alveolar edge is somewhat elevated. In theposterior half of the jaw is a dentigerous plate corresponding in sizeand shape to the pterygoid plate above and studded with the samekind of teeth. It is probably supported largely by the dentary butthe spleniaI may also take part. The articular region has two cotylicorresponding to the condyles of the quadrate above. There are noopenings on the outer side of the jaw and none can be made out onthe inner side.The axis has a short centrum with elongate pits on either side asin Naosaurus. The transverse processes rise from the neural archand the upper edge of the centrum; the posterior edge is continuedas a long ridge on the side of the centrum to the posterior edge. Theanterior face is elongate vertically but it has been crushed so that theform is obscured. The spine is low but it was very heavy, curvingforward over the anterior face; the posterior zygapophyses are largebut the anterior ones are small The posterior edge of the spine is,verv wide, extending out over the sides of the centrum.Position and Relationships.-It is most unfortunate that thevertebrae and limbs of this form are not known. The evidence of theskull shows that it has little in common with the rest of the Pelyco-sauria and that it is very far removed from the genus NVaosaurus withwhich it was most closely connected by Cope. The probable similarityof habits to Placodus has been pointed out above and a comparisonof the skulls shows many pointsshown in a comparative table:Placodus.Skull low and broad.A single temporal vacuity.Incisor teeth chisel-shaped, project-ing forward from the skull.Maxillary teeth flat and adaplted tocrushing or grinding.Posterior nares a single opening be-tween the prevomers and premaxil-laries.Palatine teeth few and large.Teeth of the lower jaw reduced to theincisors and crushing teeth.Pterygoid without external process.Interparietal and epiotic present.Occurring in the Triassic.of resemblance. These are bestEdaphosaurus.Skull low and broad.Probably two temporal vacuities.Incisor teeth approaching chisel-shapeand projecting forward from theskull.Maxillary teeth thin and sectorial.Posterior nares a single openingbetween the prevomers.Palatine teeth numerous and smaller.Lower jaw with teeth on the border aswell as the crushing teeth.Pterygoid without external process.Interparietal and epiotic present.Occurring in the Permian.There is not sufficient evidence to warrant the conclusion thatthere is an actual relationship between, Edaphosaurus and Pla-codus, but the similarity of the two is certainly very suggestive.If Placodus is a true synapsidan form, related to the Anomodontsas held by many authors, it could have no connection, genetically,with Edaphosaurus, but it must have passed through a similarstage of evolution in the growth of the palatine and dentary crush-ingteethand the loss of the teeth on the edges of the maxillaryand the dentary. Two things are worthy of note in the studyof the relations of the two: (i) It is not proven that Edapho-saurus had two temporal vacuities, though I believe it to havebeen the case. (2) The new genus Anomosaurus of v. Huene, whichhe believes to be a Pelycosaurian and which is certainly very closelyrelated to that suborder, comes from not only the same horizonI 906.] Case, Skull of Edaphosaurus. 2526 Bulletin American Museum of Natural History. [Vol. XXII ]but even from the same locality as Placodus,l and some of thevertebrm, at least, may belong to it. Should this turn out to be trueit may be that future discoveries will show that Edaphosaurus oc-cupies an ancestral position to the Placodontia.FIG. 7.-Palatal view of the skull of Placodus. After v. Huene. Lettering as in figure 2.EXPLANATION OF PLATE VII.FIG. I. Upper surface of the skull of Edaphosaurus pogonias Cope. No.4009 Am. MUS., x 2. pmx. premaxillary, n. nasal, mx. maxillary,pf. prefrontal, 1. lachrymal, pl. palatine, pt. pterygoid, f. frontal,pO. paroccipital, p. parietal, pt1. postfrontal, q. quadrate, qj.quadratojugal, sq. squamosal, psq. prosquamosal.FIG. 2.- Lower view of the same. Lettering as in figure i and; pv. prevomer,pn. posterior nares, bs. basisphenoid, bo. basioccipital, st. stapes.1 Pelycosaurier in deutschen Muschelkalk. Neuen. Jahrb. f. Min., Geol., u Paleont., BeilageBd. XX. 1905, p. 336.E;~~~

Skull of Edaphosaurus

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