THE FAUNA OF THE ARUNDEL FORMATION OFMARYLAND.
By Charles W. Gilmore.Associate Curator, Division of Paleontology , United States National Museum.
INTRODUCTION.The vertebrate fauna of the Arundel formation of Maryland haslong been a subject of interest to all workers in American Mcsozoicformations. The correlation of this fauna with the Morrison (Atlan-tosaurus, Como) beds fauna of the Rocky Mountain region by Prof.O. C. Marsh, and the later 1 and more positive confirmation of thatconclusion by Dr. R. S. Lull, has been quite generally accepted asthe correct interpretation. The present communication gives theresults of a more recent study of all known specimens from the Arun-del formation, and the conclusions reached are quite at variance tothose of my predecessors. The evidence appears to show?first, thatthe vertebrate fauna as a whole is not to be closely correlated withthat of the Morrison formation of the West; second, that it containsforms having undoubted Upper Cretaceous affinities; third, that itconsists of a combination of dinosaurian forms hitherto unknown inany fauna of this continent?that is, the intermingling of Sauropo-dous dinosaurs with those having Upper Cretaceous affinities.While the discussion of several phases of this question are neces-sarily inconclusive, due to the paucity of the materials, yet the maincontentions, I believe, can be fully maintained.SOURCE OF MATERIALS.Practically all of the vertebrate materials known from the Arundelformation of Maryland are now assembled in the United StatesNational Museum. These comprise all of the specimens collected bythe late J. B. Hatcher, in 1887 and 1888 for the United States Geolog-ical Survey; the Goucher College collection brought together byProf. Arthur Bibbins during the years 1894, 1895, and 1896; and afew single specimens that have been acquired by the United StatesNational Museum from various sources.
1 Maryland Geol. Survey, Lower Cretaceous, 1911, pp. 173-178.Proceedings U. S. National Museum Vol. 59?No. 2389. 581
582 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59.The Government materials which form the bulk of the collection,as said by Hatcher, 2 were "found in a bed of iron ore near Bladens-burg [Muirkirk], Maryland. The exact locality of the Marsh materialwas certain iron ore mines on the farm of Mr. William Coffin, andespecially in that one locally known as "Swampoodle" and situatedabout 1? miles northeast of Beltsville, on the Baltimore & OhioRailway, some 13 miles from Washington."As to the occurrence of these fossils Hatcher says:No two bones or fragments of all that material collected from the Potomac beds inMaryland were found in such relation to one another as to demonstrate that theybelonged to the same individual. In any discussion as to the affinities of these variousgenera and species of small Sauropod dinosaurs, not only the immature nature of theremains upon which they have been based, but also the scattered and disarticulatedstate in which found, must be constantly borne in mind.The above remarks as to the scattered state of the specimens applyequally well to those other remains in the collection, subsequentlybrought together by Professor Bibbins and others.THE ARUNDEL FAUNA.Our knowledge of the Arundel fauna had its beginning as early as1859, when Dr. Christopher Johnston gave the generic name Astrodon 3without description to certain reptilian teeth obtained by a Mr. Tysonfrom a bed of iron ore near Bladensburg, Maryland.In 1865 these teeth were fully described and figured as Astrodonjohnstoni by Dr. Joseph Leidy, 4 they being the first remains of aSauropod dinosaur to be named and described from North America.Twenty-three years later Prof. O. C. Marsh made the next contri-bution 5 to our knowledge of this fauna, when he established twogenera and five new species all pertaining to the dinosauria. Thesewere Pleurocoelus nanus, P. alius, Priconodon crassus, Allosaurusmedius, and Coelurus gracilis. The presence of turtle and crocodilianremains was mentioned, but it was 10 years later that Dr. O. P. Hay,described a turtle under the name of Glyptops caelatus*The next important paper dealing with this fauna was that byProf. R. S. Lull 7 in which he revised and described all of the materialsavailable at that time. Two species of dinosaurs Creosaurus potens,Dryosaurus grandis and a crocodilian reptile Goniopholis affinis weredescribed as new, and the presence of a fossil gar fish was mentionedfor the first time.
? Annals of the Carnegie Museum, vol. 2, 1903, pp. 11-13.? Amer. Journ. Dental Sci., vol. 9, 1859, p. 341.
? Smiths, Contr. Knowl., vol. 14, art. 6, 1865, pp. 102-119, pi. 13, figs. 20-23; pi. 20, fig. 10? Amer. Journ. Sci., ser. 3, vol. 25, 1888, pp. 89-94.
? Fossil Turtles of North America, Carnegie Institution, Washington, 1908, pp. 52, 53, pi. 7, figs. 1, 2.7 Kept. Geol. Survey of Maryland, Lower Cretaceous, 1911, pp. 173-211, pis. 11-20.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 583The complete fauna as recognized by Lull in 1911, and the re-vised fauna as now determined by Gilmore are shown in the twoparallel columns below:
Vertebrate Fauna of the Arundel Formation.Theropoda.Listed by Lull in 1911. Revised by Gilmore in 1921.Allosaurus medius Marsh. Dryptosaurus? medius (Marsh).Creosaurus potens Lull. Dryptosaurus? potens (Lull).Coelurus gracilis Marsh. Coelurus? gracilis Marsh.Ornithomimus affinis GilmoreSauropoda.Pleuroceolus nanus Marsh. Astrodon nanus (Marsh).Pleuroceolus alius Marsh. Astrodon altus (Marsh).Astrodon johnstoni Leidy
.
Atrodon johnstoni Leidy.Orthopoda.Priconodon crassus Marsh. Priconodon crassus Marsh.Dryosaurus grandis Lull. Crocodylia.Goniopholis affinis Lull. Goniopholis? affinis Lull.Testudinata.Glyptoj)s caelatus Hay. Glyptops caelatus Hay.Pisces.Ganoid fish
.
Ganoid fish.Undetermined fish
.
The reasons for the above changes in the 1921 list are discussedbelow under their respective headings in the order as given above.DISCUSSION OF THE MEMBERS OF THE ARUNDEL FAUNA.Order DINOSAURIA.DRYPTOSAURUS? MEDIUS (Marsh).Plate 110, fig. 2.This species was originally established by Marsh on a number ofcotypes,8 all but one, the crown of a single large tooth (Cat. No.4972, U. S. N. M.), Lull subsequently removed to the genus Dryo-saurus, as the cotypes of the new species D. grandis Lull,9 andmore recently referred by me 10 to the genus Ornithomimus. At thistime Dryptosaurusl medius rests on a single tooth shown in plate 110,figure 2. So far as the type material is concerned it will always
8 Amer. Journ. Sci., vol. 35, 1SSS, p. 93.9 Maryland Geol. Survey, Lower Cretaceous, 1911, pp. 183-186.i? Bull. 110, U. S. National Museum, 1920, pp. 119-121.
584 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59.remain a form of doubtful affinities. It is determinable as to sub-order (the Theropoda), but in the present state of our knowledgeconcerning the carnivorous dinosauria it is not determinable generi-cally, and should therefore be regarded as an indeterminate type.The few scattered bones referred to this species by Lull can beassigned, with equal propriety, to Dryptosaurus? potens Lull, foundedon a somewhat more adequate type. I have already, in the papercited above, attempted to show that two caudal vertebrae, from thedistal part of the tail formerly referred to this species, probablypertain to an Ornithomimid dinosaur, and some of the other bonesmay eventually find a similar fate in other directions.It is quite probable that these scattered elements represent morethan one kind of the large carnivorous dinosauria in this formation,but to definitely determine that fact more diagnostic materials mustnecessarily be found. DRYPTOSAURUS ? POTENS (Lull).Plate 111, fig. 2.This species was originally referred by Lull11 to the genus Creosaurus,a genus established by Marsh on materials from the Morrison forma-tion of Wyoming. In a recent paper 12 giving the results of a detailedstudy and comparison of the type with other Theropod specimensI arrived at the following conclusions:1. That the genus Creosaurus should be abandoned to become asynonym of Antrodemus.2. That the type specimen, consisting of a single vertebral centrum(see pi. 1 1 1 , fig. 2) , pertains to the caudal series and not to the presacralregion as originally determined.3. That a comparison of the type specimen with the homologouselement in Antrodemus (compare figs. 1 and 2, pi. Ill), shows suchdissimilarities as to render its assignment to that genus out of thequestion.4. That the closest resemblance of the type vertebral centrumappears to be with the caudals of Dryptosaurus aquilunguis Cope(compare fig. 2, pi. Ill, with fig. 2, pi. 114), and it was therefore provi-sionally referred to that genus.When viewed in profile the straightness of the ventral border withdistinct keel at once distinguishes this bone from all known carni-vorous dinosaurs of the Morrison formation. In Tyrannosaurus andGorgosaurus from the western Upper Cretaceous the concavity of thelower border of the anterior caudal vertebrae is markedly straighterthan in any of the Morrison Theropods, and in Dryptosawus asfigured by Cope (see pi. 114, fig. 2), from the Upper Cretaceous of
> l Lower Cretaceous of Maryland, Maryland Geol. Survey, 1911, pp. 186-187, pi. 14, fig. 4.u Bull. 110, U. S. National Museum, 1920, pp. 116-119, pi. 32.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 585New Jersey is found the nearest approach to the straight ventralborder of the specimen under consideration.Although fully recognizing the inadequate nature of the typematerial the resemblances pointed out above appear highly significant,and taken in conjunction with their similar geographical distributionleads me to believe its assignment to Dryptosawus to be the logicaldisposition of this species at this time.COELURUS? GRACILIS Marsh.Plate 110, fig. 5.Coelurus gracilis Marsh was also established on a very poor specimenconsisting of an ungual phalanx, the tip of which is missing, as shownin plate 110, figure 5.The original description is as follows:The smallest Dinosaur found in these deposits is a very diminutive carnivore,apparently belonging to the genus Coelurus. It was not more than one-half of thesize of the western species and its proportions were extremely slender. The bonesare very light and hollow, the metapodials being much elongated and their wallsextremely thin. An ungual phalanx of the manus measures about 25 mm. in lengthand 14 mm. in vertical diameter at the base. This animal could not have beenmore than 5 or 6 feet in length.One would infer from the above description that Marsh had otherbones besides the ungual, but I find none in the collection whichcould by any stretch of the imagination be so referred.Three teeth in the Goucher College collection were referred byLull to this form, two of them having come from the same locality asthe type. These, of course, have been arbitrarily associated. Thecomparison of these teeth with the tooth of Coelurus fragilis, figuredby Marsh 1! from the Morrison and which Lull has shown differ con-siderably in the almost total reduction of the crenulation of theanterior convex border, and their larger size, offers but little assist-ance in getting at the true affinities of these teeth. Furthermore, asI have shown, 14 the tooth of C. fragilis does not belong to the typematerials, it having been received at the Yale Museum some time inadvance of the type, so there is no evidence of their association.That the (type) ungual pertains to the fore foot of a small carniv-orous dinosaur there can be no question, but that it is referable tothe genus Coelurus remains to be demonstrated. In the present stateof our knowledge of the carnivorous dinosauria I doubt the possi-bility of determining the genus to which it belongs, at least with anycertainty of the correctness of the identification.A careful comparison of the type specimen has been made with allavailable carnivore unguals in the collections of the United States
" 10th Ann. Rep. U. S. Geol. Surv., pt. 1, 1S96, pi. 7, fig. 1.11 Bull. 110, U. S. National Museum, 1920, p. 128.
586 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59.National Museum and the American Museum of Natural History,from the Morrison, Lance, and Belly River formations, and thosewhich were found to resemble it most nearly were from the BellyRiver formation. No fewer than four unguals in the AmericanMuseum of Natural History collections, except for their larger size,were exact counterparts of the bone under consideration (comparefigs. 4 and 5, pi. 110). None of these, however, have been identified.One of them is illustrated here together with the type to show theirclose resemblance. While the observations recorded above may beof little moment, it appears significant that two bones from widelyseparated geological horizons should show such startling close resem-blances, especially, since the Arundel fauna contains other membersthat have unquestioned Upper Cretaceous affinities.ORNITHOMIMUS AFFINIS Gilmore.Plate 112, figs. 1 and 3; plate 113, figs. 1 and 3; plate 114, fig. 1.Ornithomimus affinis was founded 15 on a number of cotypes,consisting of an astragalus, metatarsals, and other elements of thehind feet. In 1888 16 those same bones were used by Prof. O. C.Marsh as the cotypes of the species Allosaurus medius, all of whichexcepting a tooth were subsequently referred by Lull l7 to the Ortho-poda and to the new species Dryosaurus grandis. In a recent paper 18I have shown that these cotypes do not pertain to the herbivorousdinosauria but to the carnivorous Theropoda, and in all probabilityto the genus Ornithomimus. The species name "grandis" havingbeen previously used, it became necessary to assign a new name andthe term 0. affinis was selected to designate this species.The recognition of an Ornithomimid dinosaur in the Arundel faunawas entirely unexpected for previously representatives of the familyOrnithomimidae had only been known from the Judith River, BellyRiver, Edmonton, Denver, and Lance formations of the RockyMountain region, all Upper Cretaceous, while the Arundel on thehighest authority, has been regarded of Lower Cretaceous age.Thus the range of this dinosaurian family is greatly extended bothgeologically and geographically.Since these cotypes have been described in detail in a recent paper l9it appears unnecessary to do more here than to call attention to thosefeatures which demonstrate the Theropod nature of these bones,followed by a summary of the reasons for assigning them to thegenus Ornithomimus.
is Bull. 110, U. S. National Museum, 1920, pp. 137.
?6 Amer. Journ. Sci., vol. 35, 1S88, p. 93.17 Lower Cretaceous, Geol. Survey of Maryland, 1911, pp. 183-186.w Bull. 110, U. S. National Museum, 1920, pp. 137-142.w Idem, pp. 137-142.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 587In the parallel columns below the Theropod nature of the cotypesare clearly demonstrated by contrasting their important structuralfeatures with the homologous bones of the Orthopod hind foot.Theropod characteristics of the cotypes ofOmithomimvs ojfniis. Characteristics of the Orthopod pts.1. Astragalus with ascending process. 1. Ascending process always al sent.2. Astragalus narrow fore and aft as com- 2. Astragalus wide fore and aft, as com -pared with transverse diameter. pared with transverse diameter.3. Articular surface on distal end of 3. Extent of articular surface on frontmetatarsal III, extending higher on front and back of distal end of metatarsal III,than on back of bone. sul. equal.4. Unguals of hind feet compressed. 4. Unguals of hind feet depressed.5. Lateral pits on distal ends of foot 5. Lateral pits on distal ends of footbones deep and their borders well defined, bones shallow or wanting, their bordoiswhen present, illy defined.6. Articular ends of foot bones, having 6. Articular end of foot bones, usuallywell finished surfaces. lacking refinement of their surfaces.The Ornithomimid character of these cotypes was established by adirect comparison with the foot bones of the fine skeleton of Orni-ihomimus (Struthiomimus) alius Lambe and other Ornithomimidmaterials in the American Museum of Natural History, New York.In every instance such close resemblances were found as to leavelittle doubt of their generic identity.For the present purposes it is thought the similarities of thesebones may be most clearly demonstrated by showing homologousbones of the Arundel and Belly River Ornithomimids side by side.In plates 112 and 113 are thus illustrated a number of these bonesreproduced here from photographs. Their close similarities, in someinstances, down to the minutest details appears to me to be sufficientto demonstrate their pertaining to animals of congeneric relationship.SAUROPODOUS DINOSAURS.Prof. R. S. Lull has given such a thorough and detailed discussion 20of the Sauropod Dinosaur remains from the Arundel formation thatfor the present purposes a detailed discussion of them appears un-necessary. After a thorough examination of the materials I fullyconcur in his conclusions. Lull recognized three species of Sauro-podous dinosaurs from the Arundel Astrodon johnstoni, Pleurocoelusnanus, and P. altus. Hatcher contended 21 that
?
Since these remains were found in essentially and perhaps identically the samelocality and horizon, and, in consideration of the very great similarity which theyexhibit, there appears no good reason for considering them as pertaining to eitherdifferent genera or species. Astrodon johnstoni Leidy, having priority, should, there-fore, be retained, while Pleurocoelus nanus would become a synonym of that genusand species.
20 Lower Cretaceous, Md. Geol. Survey, 1911, pp. 188-204.51 Annals Carne. ie Museum, vol. 2, 1903, pp. 11-12.
588 PROCEEDINGS OF THE NATIONAL MUSEUM. vuu 50.Lull observes:I am inclined to agree with Hatcher in considering Astrodon and Pleurocoelussynonyms, hut not in the synonym of the species, P. nanus with Astrodon johnstoni:* * * Pleurocoelus altus, on the other hand, is represented by but few hones, andcould readily have been the possessor of teeth like those of Astrodon johnstoni. * * *It is therefore quite possible that Pleurocoelus altus should be considered as synony-mous with Astrodon johnstoni, in which case the latter name would take precedence.It eeems preferable, however, in view of the rarity of the remains, to let the matterrest in abeyance until further proof is obtained.The materials clearly show the presence in the Arundel of a largeand small species of the Sauropodous dinosauria, and while I fullyconcur in Lull's view of the continued use of all the named species,I think it preferable to assign all to the genus Astrodon, which clearlyhas priority. PRICONODON CRASSUS Marsh.Plate 110, fig. 3.Priconodon crassus was founded by Marsh 22 on a single tooth (Cat.2135, U. S. N. M.) (see pi. 110, fig. 3), his original description beingas follows:The existence of another herbivorous dinosaur in the same horizon of the Potomacformation is indicated by a number of fragmentary remains, the most characteristicof which is the tooth figured below. This may be regarded as the type specimen.Although resembling somewhat the teeth of Diraconodon [Diracodon] from the Jurassicof the West, it is quite distinct. It has the narrow neck, swollen base, and flattenedcrown of that genus, but the serrated edges meet above at a sharp angle, instead offorming a wide curve at the apex. The surface shown in fig. 7 [pi. 110, fig. 3, left] ismuch worn by the opposing tooth. In figure 9 [pi. 110, fig. 3, right] the pit formed bythe succeeding tooth i3 seen near the top of the fang.Lull, in his study 23 of the Arundel vertebrates, consisting of thetype and subsequently discovered materials, recognized five otherteeth pertaining to Priconodon crassus, and a vertebral centrum wasquestionably referred by him to this species. The latter I regard aspertaining to the sacrum, and have tentatively assigned 24 it to Ornitlio-mimus.Lull recognized the resemblance of these teeth to those of Paleoscin-cus costatus Leidy. He says
:
This tooth [the type] resembles somewhat that of Palaeoscincus costatus Leidy,from the Judith River beds, though the type of Palaeoscincus is slightly smaller thanthat of the present species. The swelling shoulder in Priconodon is more prominentand rounded than in Palaeoscinus, and in the latter the cusps are much sharper andmore prominent, though less numerous on one edge of the crown. The median ridgeof Priconodon is also lacking.In his concluding remarks Lull sa}7s:The tooth of Priconodon comes nearest Leidy's Palaeoscincus from the Judith River,to which it could readily be ancestral, as the evolutionary tendency on the part ofthe Orthopoda is to increase the number and decrease the size of the teeth.w Amer. Journ. Sci., ser. 3, 1S88, vol. 25, p. 93, figs- 7-9.? Report Maryland Geol. Survey, Lower Cretaceous, 1911, p. 208." Bull. 110 U. S. National Museum, 1920, p. 142.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 589After comparing the type and other teeth of Priconodon with theteeth of Palaeoscincus and Stegosaurus in the National Museum col-lections, I fully concur in Lull's conclusions as to their close resem-blance to those of Palaeoscincus, but do not see that they are anycloser to the latter than to Stereocephalus tutus Lambe,25 also anUpper Cretaceous form from the Belly River of Alberta, Canada.In size, method of wear, and general characteristics the teeth ofPriconodon certainly indicate closer affinities with the armored dino-saurs of the Upper Cretaceous than with Stegosaurus of the Morrisonformation.Although our classification of the American armored dinosauria issomewhat in confusion at the present time, the discoveries of recentyears, much of the material as yet undescribed, shows that theUpper Cretaceous forms belong to families distinct from the MorrisonStegosauridae. Whether the Nodosauridae, Ankylosauridae, orScelidosauridae all represent valid families I am not prepared to say,but it is to one of these, probably the Nodosauridae, that Priconodonshould be assigned rather than the tall plated Stegosauridae asclassified by Hay, 26 Lull, 27 and others.Order LORICATAFamily CROCODYLIDAE.GONIOPHOLIS? AFFINIS Lull.Plate 110, fig. 1.This crocodilian was founded on very scanty materials, the se-lected type being the crown of a single tooth (Cat. No. 8452, U.S.N.M.)(pi. 110, fig. 1), though other teeth and part of a dermal scute werementioned in the original description. 28Lull points out that while the teeth resemble, in size and shape,those of crocodiles from the Morrison formation, yet they differ by
"having secondary ridges between the main ridges on the proximalportion of the crown." The sculpturing of the scute is also shownto be coarser than on any of those from the Morrison of the West.In view of the present state of our knowledge concerning theextinct Crocodilia I do not believe it is possible to definitely deter-mine the genus to which a form based on such meager materialsbelongs, and until more diagnostic specimens are found it will un-doubtedly remain a species of uncertain affinities. At this time ithas no apparent value for the correlation of this fauna and shouldbe eliminated from such consideration. Except for showing thepresence in the Arundel fauna of an extinct crocodilian these frag-mentary specimens have but little significance.
15 Contributions Canadian Paleontology, vol. 3, pi. 2, 1902, pp. 55-57.?s Bull. 179, U. S. Geol. Surv., 1902, p. 4%." Rept. Md. Geol. Surv., 1911, Lower Cret., p. 207.? Idem, pp. 210-211, pi. 20, fig. 7.
590 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59.Order TESTUDINATA.Family PLEUROSTERNIDAE.GLYPTOPS CAELATUS Hay.There have been no additional discoveries of turtle remains in theArundel formation since Dr. O. P. Hay described 29 Glyptops caelatusin 1908, so that our knowledge of this form rests entirely on the type,a fragmentary specimen, from which little information can be obtainedas to its relationships to the other species of the genus. At my requestDoctor Hay was kind enough to reexamine the type materials for thepresent study and reports as follows:T can not say whether Glyptops caelatus is more or less closely related to the Morrisonforms than to those from the Lower Cretaceous. In comparing the Morrison andArundel faunas I think I would not put G. caelatus in the balance.From the above statement it appears, therefore, on the highestauthority, that the Arundel turtle remains can not contribute any-thing of value to the present discussion of this fauna.CLASS PISCES.At this time the known fish remains of the Arundel fauna consistof a single scale of a Ganoid and a tooth which, in the sculpturingof its flattened grinding surface, slightly resembles those of PtycJiodusfrom the Niobrara formation of the Upper Cretaceous. It probablyrepresents an undescribed form. The specimen (Cat. No. 10294,U.S.N.M.) was found by Mr. C. Englehart in 1894 near Contee,Maryland. SUMMARY.In the preceding review of the several genera and species of fossilvertebrates that comprise the known fauna of the Arundel formationof Maryland, it is apparent that most of them were established onvery meager and, in some instances, inadequate materials. Theproper treatment of such more or less indeterminate forms has longbeen one of the difficult problems in modern vertebrate paleontology-In the handling of this fauna in the past, but little discriminationhas been made as to the adequate or inadequate nature of the speci-mens on which the names were based. To regard all members of afauna as generically and specifically determinable, when from thevery character of the type specimens they can only be determined asto order or family, is an erroneous practice.While in making up faunal lists it is necessary to include suchforms, it should always be specified to what extent such questionablegenera and species are determinable. , The neglect of such a precau-tion has in the past sadly misled workers in their final conclusions
so Fossil Turtles of North America, 1908, pp. 52, 53, pi. 7, figs. 1, 2.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 591where faunal lists have been used to prove the synchronous natureof widely separated formations.The contention of Marsh,30 corroborated by Hatcher,31 and thelater even more positive assertion of Lull 32 that the Arundel fauna
"correlates the beds wherein they are found absolutely with theMorrison (Como) of the west," is a conclusion which this recent studyshows can not be maintained.Forms that have been founded on single teeth or a single bone,especially in the reptilia, do not permit of an accurate diagnosis ofthat form, and neither does it permit of a satisfactory comparisonwith other specimens. Some of these, as the types of Coelurus gracilis,Dryptosaurus? medivs, and Dryptosaurus? potens, are certainly deter-minable as to suborder, possibly family, but are not surely deter-minable generically, as the genera of carnivorous dinosaurs are nowdistinguished. The remaining Theropod, Ornithomimus affinis, iscertainly distinguishable as to family, possibly as to genus.While the synonymy of the two genera and three species of theSauropoda found in the Arundel fauna is somewhat uncertain at thistime, the materials are entirely sufficient on which to characterize atleast one good genus and two species, and for the purposes of thepresent discussion this appears entirely adequate.The Orthopoda is represented by the single genus and species,Priconodon crassits, based on a single tooth. At this time our knowl-edge of the armored dinosauria is such that we do not know whetherthe teeth are diagnostic of genera or not. Taking into account thehighly specialized character of the teeth in the few known forms, itwould appear that perhaps in this group of reptiles, when sufficientlywell known, it will be found that the teeth are diverse enough in theircharacters to at once tell to which particular genus they pertain.The above review of determined forms shows the evidence for thecorrelation of the Arundel fauna with the Morrison, rests entirely onthe presence of Sauropodous dinosaurs in both formations, and theapparent occurrence of one genus Astrodon (Pleurocoelus) common toboth, although a review of the Morrison materials identified as per-taining to Astrodon (Pleurocoelus) by both Marsh and Hatcher isscanty and not altogether reassuring as to the soundness of theiridentifications. It is my conclusion that, with the exception ofAstrodon (Pleurocoelus) , there is not another one of the named dino-saurian specimens from the Arundel which at this time can be said tobe closely allied to any of the Morrison forms.On the other hand the presence of an Ornithomimid dinosaur per-taining to the family Ornithomimidae, which has never before been
30 Amer. Journ. Sci., vol. 11, 1896, pp. 43?-436.31 Annals Carnegie Museum, vol. 2, 1903, pp. 13-14.81 Lower Cretaceous, Geol. Survey of Maryland, 1911, p. 178.
592 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 59known below the Upper Cretaceous (Belly River) ; an armored dino-saur, Priconodon crassus, which Lull, correctly recognizes as havingits closest affinities with Palaeoscincus of the Upper Cretaceous; acarnivorous dinosaur having a caudal vertebra most nearly resemblingthe Upper Cretaceous Dryptosaurus from New Jersey; and the smallerTheropod Coelurus? gracilis based on a claw of the fore foot, thatexcept for its much smaller size has its exact counterparts in collec-tions from the Belly River formation.Summing up the evidence, such as it is, we have on the one handin the Arundel the presence of Sauropodous dinosaurs which havebeen generally considered as not having survived after the close ofthe Morrison, and on the other hand one family of known UpperCretaceous occurrence, and at least three other forms which havetheir closest resemblances with Upper Cretaceous dinosaurs. Imper-fect as it is, the weight of the vertebrate evidence would appear tofavor a higher position in the geological scale than has been attributedthis fauna in the past.In this connection it is of interest to find that this conclusion ismore in accord with the paleobotanical evidence, as interpreted byBerry, than the previously accepted correlation of the Arundel withthe Morrison. Berry,33 in comparing the floras of the Arundel andKootanie of Montana, observes:The two floras have a great many elements in common, and upon the basis of thefloras alone the conclusion would be reached that the base of the Kootanie was approxi-mately the same age or slightly older than the base of the Patuxent (a formation con-formably underlying the Arundel). When the faunas are considered it develops thatthe Morrison fauna, which is considered by many paleontologists to be of Jurassicage, is found conformable beneath the beds containing the Kootanie flora, which is ofunquestioned Lower Cretaceous age. Along the Atlantic seaboard this is reversedand the bulk of the flora corresponding to that of the Kootanie underlies beds con-taining a large representation of the Morrison fauna, and which also has been con-sidered to be Jurassic age by Marsh and others.West.
No. 2389. FAUNA OF THE MARYLAND ARUNDEL?GILMORE. 593Berry's conclusion, based alone on the evidence of the floras, thatthe Patuxent and Kootanie formations are of approximately thesame age, as graphically shown in the foregoing diagram, is now fullyin accord with the vertebrate evidence as indicating a higher positionin the Lower Cretaceous for the Arundel formation than has beenpreviously given it. The only difference between these two lines ofevidence is that, whereas "the Patuxent-Arundel floras are essen-tially a unit of early cretaceous age whose affinities all lie with thefloras which preceed them," the affinities of the Arundel vertebratefauna is divided, the Sauropod dinosaurs having close relationshipswith the preceding fauna and all others apparently having theirclosest affinities with those faunas which succeeded the Arundel.EXPLANATION OF PLATES.Plate 110.Fig. 1. Tooth of Goniopholis"? affinis Lull. Type. Cat. No. 8452, U.S.N.M. Naturalsize after Lull. See p. 589.Fig. 2. Tooth of Dryptosavrusl medius (Marsh). Type. Cat. No. 4972, U.S.N.M.Natural size. Lateral view. See p. 583.Fig. 3. Tooth of Priconodon crassus Marsh. Type. Cat. No. 2135 U.S.N.M.Natural size. Outer, edge, and inner views. After Marsh. See p. 588.Fig. 4. Ungual phalanx of the manus of an unidentified dinosaur from the BellyRiver formation, Upper Cretaceous of the Red Deer River, Alberta, Canada. Cat.No. 5387, Amer. Mus. Nat. Hist. Twice natural size. Lateral view. See p. 586.Fig. 5. Ungual phalanx of the manus of Coehtrus? gracilis Marsh. Type. Cat.No. 4973, U.S.N.M. Twice natural size. Lateral view. With the exception ofthe difference in size, note the close similarity of figures 4 and 5. See p. 585.Plate 111.Fig. 1. Anterior caudal centrum of Antrodemus valens Leidy. From the Morrisonformation of Wyoming. Cat. No. 8367, U.S.N.M. About one-half natural size.Viewed from the left side. See p. 584.Fig. 2. Anterior caudal centrum of Dryptosaurus? potens (Lull) from the Arundelformation of Maryland. Type. Cat. No. 3049, U.S.N.M. About one-half naturalsize. Viewed from the left side. Compare the straight ventral border of this bonewith the anterior caudals of Dryptosaurus aqvilunguis, pi. 114, fig. 2. See p. 584.Plate 112.Fig. 1. Second phalanx digit III, right, of Ornithomimus affinis Gilmore, Cotype.Cat. No. 5703, U.S.N.M. Anterior view. Natural size. See p. 586.Fig. 2. Second phalanx digit III, right, of an Ornithomimid dinosaur from theBelly River formation, Upper Cretaceous, Alberta, Canada. Cat. No. 5201, Amer.Mus. Nat. Hist. Anterior view. Natural size. See p. 586.Fig. 3. Proximal phalanx of digit II, left Ornithomimus affinis Gilmore, Cotype.Cat. No. 5453, U.S.N.M. Anterior view. Natural size. See p. 586.Fig. 4. Proximal phalanx of digit II, left, of an Ornithomimid dinosaur, same asfig. 2. Natural size. See p. 586.27177?21?Proc.N.M.vol.59 38
594 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59.Plate 113.Fig. 1. Second phalanx digit IV, right, of Ornithomimus affinis Gilmore, Cotype.Cat. No. 8456, U.S.N.M. Anterior view. Natural size. See p. 586.Fig. 2. Second phalanx digit III, right of an Ornithomimid dinosaur from the BellyRiver formation, Upper Cretaceous, Alberta, Canada. Cat. No. 5201, Amer. Mus.of Natural History. Anterior view. Natural size. See p. 586.Fig. 3. Distal portion of metatarsal III, right of Ornithomimus affinis Gilmore, Cotype.Cat. No. 5684, U.S.N.M. Anterior view. Natural size. See p. 586.Fig. 4. Distal portion of metatarsal III, left of an Ornithomimid dinosaur from theBelly River formation, Upper Cretaceous of Alberta, Canada. Cat. No. 5201, Amer.Mus. Nat. History. Anterior view. Natural size. See p. 586.Plate 114.Fig. 1. Distal portion of metatarsal II, right, of Onithomimus affinis Gilmore.Cotype. Cat. No. 5704, U.S.N.M. Lateral view. Natural size. See p. 586.Fig. 2. Anterior caudal vertebrae of Dryptosaurus aquilunguis Cope. Very muchreduced. Compare with fig. 2. Plate II. After Cope. See p. 584.
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 59 PL. 110
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Fauna of Arundel Formation of Maryland.FOf? EXPLANATION OF PLATE SEE PAGE 594.
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