y UWiVEHSn Y CF ILUNOIS LIBRARY ATURBANA-CHAMPAIGN GEaOGY The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. UNIVERSITY OF MMMniS LIBRARY AT URBANA-CHAMPAIGN OCT f 3 L161 — O-1096 I FIELDIANA • GEOLOGY Published by FIELD MUSEUM OF NATURAL HISTORY Volume 16 March 22, 1968 No. 8 Cymaprimadontidae A New Family of Insectivores John Clark ASSOCIATE CURATOR, SEDIMENTARY PETROLOGY I. Introduction During the summer of 1965, Mr. K. Kietzke of the Field Mu- seum staff collected a partial right mandible of an animal which is, even on cursory examination, a new form. The specimen occurred near the top of the Crazy Johnson Member of the Chadron For- mation in South Dakota. The matrix is a slightly-cemented ben- tonitic mudstone with abundant, very fine sand grains. Paleogeo- graphically, the fossil occurred approximately a mile north of the northern edge of the zone of channel-fill sediments designated the Red River Valley (Clark, 1937). The bone is soft and white, with pale olive enamel on the teeth. Unfortunately, crystalline calcite fills many of the cracks and cav- ities, and permeates even the most intimate structure of the bone, which greatly increased the difficulties of preparation and X-ray photography. Subsequent search of the Museum's collection disclosed a left mandible, UC 349, of a form related to but not congeneric with the first. This was in the collection recently acquired from the Walker Museum. Unfortunately this second specimen, collected by Baur in 1894, has as field data: "Oligocene of South Dakota, White River Badlands." The matrix is a fine sand, better cemented and slightly coarser than that of the Chadron specimen. The bone is hard and dark gray with a limonite incrustation, and the single tooth preserved is dark brown. X-ray reveals limonite filling the pulp cavities of the tooth roots. Preservation resembles that of the Lower Nodular Zone, Scenic Member, Brule Formation; as will be devel- Library of Congress Catalog Card Number: 68-21 23 4 £OLOGlUBeNa JULUB68 imn 242 FIELDIANA: GEOLOGY, VOLUME 16 oped later, the anatomical characters also suggest that this sec- ond jaw is younger than the first. However, I have seen bone and preservation of this sort occasionally in the Peanut Peak Member the Chadron. The specimen should be regarded as of Oligocene age, probably Orellan (Brule), but possibly late Chadronian. In view of the problematical age plus the fact that only the dental ramus and M3 are preserved, I shall describe this second specimen without giving it a generic and specific name. It will be used to aid in delimiting the new family. Figures 3-6 were drawn by Dr. T. Perenyi; Figures 1 and 2 are by the author. II. Description Order Insectivora The supra-familial taxonomy of the numerous families, both fossil and recent, previously grouped within this order, is in such a state of flux that only a specialist can form significant judgments. The Early Tertiary and Recent families which seem most closely related to the new one proposed here have been variously classified, but have not previously been regarded as closely related to each other. It seems most practical, therefore, to describe the new family, indicate its possible relationship to others, and refer it to the Insec- tivora. This leaves to specialists the evaluation of relationships in suprafamilial classification. Family CYMAPRIMATONTIDAE, new family Known age and geographic distribution:- — Early to ? Middle Oligo- cene, South Dakota. Type genus: — Cymaprimadon, new genus. Family characters: — Large for insectivores, about the size of mod- ern Lutra or Lynx, mandible low, thick, extremely massive; posterior mental foramen very large, postero-ventrally directed, beneath the P4-M1 inter-alveolar partition; a curved, longitudinal groove on the latero-ventral side of the dental ramus; mandibular sym- physis small and narrow; symphyseal surfaces unsutured and almost flat; inferior cheek-tooth row strongly arched into an open sigmoid; one lower incisor enlarged, procumbent, with enamel distribution restricted and a prominent median groove; other incisors reduced or absent; canine reduced; Pi absent; P2 reduced, P3 larger, P4 the m CLARK: CYMAPRIMADONTIDAE A 243 HEAVY EfiAMEL LI&HT ENAMEL Fig. 1. Cross-sections of incisor of Cymaprimadon kenni: A, Slightly behind alveolar rim. B (Hypothetical), near tip of tooth. longest of the cheek-tooth series ; Mi-Ma progressively smaller; pos- terior roots of cheek teeth large, round; anterior roots smaller, flattened antero-posteriorly; molar paraconids reduced but present; hypoconid large, developing toward a blade; entoconid and hypo- conulid greatly reduced; root of enlarged incisor extended back to beneath posterior root of P3; mandibular canal high in jaw. Genus Cymaprimadon,^ new genus Type species: — Cymaprimadon kenni,- new species. Type specimen of species: — Field Museum no. PM 9567, a right mandibular ramus with M3 and the greater portion of an enlarged incisor. Since only this one specimen of the genus species is known, generic and specific characters are not separable. Geologic horizon: — Top of Crazy Johnson Member, Chadron For- mation, Lower Oligocene. Locality:~NW \i of NE 3^, sec. 25, T 3S, R lOE, Pennington Co., South Dakota. Northeast face of the Finney Breaks. > From Kvy.a., a wave or furrow; primus, first; o5i,>v, a tooth, in reference to the groove in the enlarged incisor. * Named in honor of Mr. Kenneth Kietzke, who found the type specimen. 244 FIELDIANA: GEOLOGY, VOLUME 16 Generic and specific characters: 1. Measurements as in Table 1. 2. Dental formula= ?3 _ i _ 3 _ 3. 3. Ii reduced, probably absent; I2 greatly enlarged, procumbent; I3 reduced, probably absent. 4. I2 enamel distributed as in Figure 1, and very thin. A complex pattern of fine, vermiform crenulations developed on the enamel surface (fig. 2). 5. Alveolus for I2 extending back to beneath the anterior alveolus for P4. 6. Cheek-tooth series continuous, crowded, without diastemata, from I2 to M3. 7. M3 trigonid low, less than twice the height of talonid, meas- ured from the enamel border. 8. Protoconid largest, paraconid medial and smallest; trigonid cusps slightly compressed at points, to enclose a tiny basin. 9. Talonid a very shallow, flat-bottomed basin, sloping strongly mesio-anteriorly. The large hypoconid rises but little higher than this basin, standing almost on the midline of the tooth with a ridge extending forward to the postero-internal base of the protoconid. The entoconid and hypoconulid are reduced to tiny nubbins on the posterior part of the low ridge which forms the postero-internal rim of the basin. 10. Tiny accessory cuspule on the postero-external side of the hy- poconid. 11. Tiny accessory cuspule on the mesio-posterior wall of the met- aconid. 12. Small but definite anterior cingulum at base of protoconid ; ob- scure cingular prominence at base of paraconid ; internal cingu- lum at base of metaconid; the three cingula separated from each other. 13. A prominent shelf around the alveoli of the molars and P4, and heavy crests at the ends of the premolar interalveolar partitions. 14. Posterior mental foramen large, as a family character; anterior to this a row of smaller foramina, probably individually vari- able in detail. 15. Protuberant muscle scars on ventral border of ramus below M3 and below Pi. 1 DENTINE ROOT PULP CAVITY Fig, 2. A, Drawing of enamel pattern of incisor, greatly enlarged. B, Photo- graph of same. 245 246 FIELDIANA: GEOLOGY, VOLUME 16 16. Rugose area on side of chin. 17. Bone surface generally marked by widely spaced, tiny, pos- teriorly directed pores, from which grooves 1-5 mm. long ex- tend backward, roughly parallel to the elongation of the bone on which they occur. New But Unnamed Genus and Species Specimen upon which description is based: — Field Museum speci- men UC 349 (formerly in the collection of the Walker Museum, University of Chicago) . The known stratigraphic occurrence is Oligocene; probably the specimen is from the Scenic Member of the Brule Formation, but possibly it is from the Peanut Peak Member of the Chadron For- mation. The locality is "White River Badlands, South Dakota." Since this expression was used by early collectors to mean "Badlands of the White River Formation" (now group), rather than "Bad- lands in the drainage area of the White River," the locality data should not be interpreted to exclude Cheyenne River and Bad River drainage basins. TABLE 1 Dimension PM 9567 UC 349 Depth of mandible below anterior root of Mi 12.6 15.6 Thickness of mandible below anterior root of Mi 8.5 10.5 Anterior rim of temporal fossa to posterior rim of posterior mental foramen 20.0 23.1 Cheek-tooth series, C-M3 alveoli 41 .4 Cheek-tooth series, P4 - Ms alveoli 30.5 35.4 Ml -Ms alveoli 20.6 24.3 P4 alveolus, antero-posterior 9.5i 10.2 Ml, alveolus, antero-posterior 7.5 7.5 M2 alveolus, antero-posterior ! 6.8 6.9 Ms, length 5.6 7.8 Ms, breadth 4.4 5.8 Ms, height, enamel rim-top of protoconid 4.9 6.4^ Ms, height, enamel rim-top of metaconid 4.0 5.6 Ms, height, enamel rim-top of hypoconid 3.3 4.7 1 Slightly too large, due to breakage and laboratory repair. 2 Estimated, — tip broken. Table 1 reveals that this specimen represents an animal much larger than Cymaprimadon kenni. The individual had, apparently, lived to a very slightly more advanced age than had the type of C. kenni, because M3 is fully erupted. M3 of C. kenni has the enamel CLARK: CYMAPRIMADONTIDAE 247 border a little below the alveolar rim. In neither case is there any trace of wear. Both individuals had apparently attained approx- imately full size shortly before their death. The similarity of growth stage makes it probable that, with the exceptions noted below, dif- ferences between the two specimens are individual or generic rather than developmental. Significant characteristics of specimen UC 349: 1. Measurements as in Table 1. 2. Dental formula= i _ o _ 2 — 3 3. Enlarged incisor alveolus extends back to beneath posterior root of P3; posterior wall consists of spongy bone apparently formed shortly before the individual's death. 4. Cheek-tooth series crowded, continuous. Little or no room for Ci, Pi_2, between the enlarged incisor and P3; probably these teeth were missing. 5. P3 reduced relative to the corresponding tooth in Cymaprima- don kenni. 6. M2 and M3 of equal size; M4 slightly longer. Pi longest in the cheek-tooth series but proportionally shorter than in C. kenni. 7. M3 trigonid low; height 62% of the length of the tooth, com- pared with 83% in C. kenni. 8. M3 protoconid very slightly larger than metaconid. Paraconid reduced to a sloping prominence connected to the anterior ridge of the protoconoid; a deep, medio- ventrally trending groove between the paraconid and metaconid. Protoconid and metaconid cusps slightly compressed at tips, but form no basin due to the reduction of the paraconid. 9. M3 talonid consists of a heavy, blunt blade, rising posteriorly to the hypoconid as its cone-shaped terminus. The remaining conules form a denticulated posterior portion of a heavy in- ternal rim which does not enclose a basin because it is not ap- preciably higher than the area within it. A heavy, low ridge extends down the linguo-posterior wall of the hypoconid to a denticle on the rim, but does not directly join it. 10. There is a small accessory cuspule on the mesio-posterior wall of the metaconid, as in C. kenni, but none on the hypoconid. 11. A very broad, low, heavy cingulum forms a straight wall across the anterior face of M3. Unlike C. kenni, no other cingula occur. 248 FIELDIANA: GEOLOGY, VOLUME 16 Fig. 3. Lateral view of jaws: A, C. kenni. B, UC 349. 12. The shelf and crests aroung the alveolar borders are even more prominent than in C. kenni. 13. The protuberant muscle scars of C. kenni are absent in UC 349; otherwise the foramina and jaw characters preserved resemble those of C. kenni. In most respects, this animal represents a genus evidently more advanced along the generic trend of the family than is Cymaprim- adon. The increase in overall size and weight, further reduction of the paraconid, further alteration of the talonid to a shearing blade based upon the hypoconid, and apparent further reduction of the anterior cheek-tooth series may all be regarded as changes carrying the Cymaprimadontidae further from [whatever was their ancestral group. The development of a heavy anterior cingulum and suppression of the other two partial cingula presumably have the same significance. The degree of specialization suggests, as does the type of preservation, that UC 349 represents a genus later in time (probably Orellan) than the middle Chadronian Cyma- primadon. Fig, 4. Vertical view of jaws: A, C. kenni. B, UC 349. B Fig. 5. Lingual view of jaws: A, C. kenni. B, UC 349, 249 250 FIELDIANA: GEOLOGY, VOLUME 16 III. Soft anatomy and probable way of life of Cymaprimadontids The symphysis in C. kenni makes a 30° angle with the axis of the mandible. The skull must have been approximately 45-50 mm. wide at the mandibular condyles. Judging from the weight of the bone and the massive muscle scars, the head was probably a great deal wider. The general head proportions were probably nearly those of an otter or lynx, with large temporal and masseter muscles compensating by their bulk for the undoubtedly narrower calva- rium of Cymaprimadon. Strong outward angulation of Mi and the lower premolars sug- gests than the anterior part of the palate was broad. Some sort of active, well-muscled labial apparatus is indicated by the rugose area on the anterior surface of the jaw; adequate blood was supplied through the large mandibular canal and short, wide-diameter mental foramina. Whatever the labial apparatus was, it presumably func- tioned in connection with the use of the unique I2. I2 poses a real problem. Great enlargement, high specialization in shape, and the development of a unique enamel decoration all indicate that the tooth functioned in a distinctive manner extremely important to the animal. The tooth must have tapered distally to a long, sharp, triangular point with an internal groove and a rounded external side. The right and left incisors together probably pro- duced a sharp, procumbent point with a cross-section as shown in Figure 1,B, rounded ventrally and marked by a tube with a dorsally open slot. Such a dental structure, with thin, discontinous enamel areas, is obviously designed for only one purpose — piercing a soft, non- abrasive object. Any normal masticatory function is impossible, for it. The tube is designed for the passage of liquids, either into or out of the animal's mouth. The first alternative, that the tube is part of a suction apparatus, requires that the animal use it to suck in either vegetable juices or blood. The only vegetable juices available to teeth so delicate would be the juice of soft-fleshed fruits. A tube so narrow would be of little use, and would almost certainly become plugged with fiber. Fur- thermore, the cheek-tooth dentition and heavy jaw musculature are not those of an innocently frugivorous animal. Judging from the size and alignment of the alveoli, P4 functioned as a reasonably I B Fig. 6. Vertical view of M3: A, C. kenni. B, UC 349. 251 252 FIELDIANA: GEOLOGY, VOLUME 16 efficient carnassial tooth, and even M3 is constructed for effective dissectorial mastication. Vampirism offers an even less satisfactory alternative utilization of these teeth. The two together would form a sharp-pointed but very short half-cone-shaped weapon, with a base at least 20 mm. broad. No animal could possibly sit quietly unnoticing while such an object was rammed into its body, and the open tube could not possibly function during the ensuing struggle. Since this dental apparatus would not effectively ingest liquid food, the remaining possibility is that it served to inject something. Solenodon, the only other known mammal with a similarly grooved tooth, has been shown to be venomous (Rabb, 1959), and to use its grooved but heavily-enamelled incisors as fangs for insertion of its venom. In Cymaprimadon, the particular gland specialized for venom was probably either the sublingual or the submaxillary, both of whose ducts discharge appropriately at the base of the incisors. Use of the incisor tube to transmit venom to its victims would be effective. Corollary to this use would be the development of a heavy maxillary root of the zygomatic arch, probably accompanied by an eversion of the arch to a feloid position. The masseter would then occupy an almost fore-and-aft position, and would drive the mandible forward. Heavy scars along the base of the mandible, presumably in part for the insertion of the digastric, suggest that Cymaprimadon was also able to withdraw its weapon with some vigor. These musculoskeletal adaptations are, of course, conjec- tural. Confirmation must await discovery of a skull. If Cymaprimadon was venomous, it must also have been an active carnivore. Such an apparatus would be entirely wasted on beetles and grasshoppers. The cheek-tooth dentition also suggests a car- nivorous habit. Whether Cymaprimadontids preyed chiefly upon fish and amphibians, or upon forest-dwelling terrestrial mammals, or on birds and arboreal mammals, is largely conjectural. The paleo- geographic location of the type of C. kenni, and the matrix of UC 349, suggest that they lived away from the stream channels proper but close enough that they certainly inhabited forests rather than savannah plains or prairies. Their rarity as fossils might be a func- tion of arboreal existence, or might simply indicate that they were rare elements of the fauna. In any event, a carnivorous insectivore weighing at least several pounds, with a head as big as an otter's and a highly effective toxic I CLARK: CYMAPRIMADONTIDAE 253 fang, must have been a frightening member of the predatory com- munity, IV. Relationships Determination of the relationships of the Cymaprimadontidae is attended by the difficulties usual to insectivore classification: fragmentary materials plus the difficulty of distinguishing geneti- cally related characters from parallel or convergent characters. A search for earlier related or ancestral forms leads at once to the Pantolestidae. Both families are large for insectivores, with massive mandibles. More significantly, both have cheek teeth small in proportion to the jaw, molars with reduced paraconids and relatively short trigonids, P4 the longest tooth in the series, and a large, short posterior mental foramen. The large canines and small incisors of the Pantolestidae obviously exclude them from a directly ancestral position, but the two families might well represent succes- sive divergences from a common stem. Possible descendants are unknown as fossils. However, com- parison with Solenodon, which has been drawn earlier on a purely functional basis, reveals a fair number of resemblances and no single conclusive difference. Both are large for insectivores. In both, the mandibular canal is large and placed high in the jaw. The symphysis in both extends back to a position beneath P3. In both, the canine is greatly reduced and an incisor (I2 in Solenodon and probably in Cymaprimadon) is grooved and enlarged. In both, apparently, venom was developed and used for predation. An equal number of equally impressive differences also becomes apparent. Solenodon has an exceedingly long, narrow skull rather than a massive one. I3 is present. P4 is not quite so long as Mi. The molars do not decrease in length posteriorly. The paraconids of the molars almost equal the metaconids in height, and lie on the lingual side of the tooth rather than in the middle. The talonid consist of a ridge and an open basin, as in Cymaprimadon, but in Solenodon the ridge connects to the metaconid and the basin is labial to it, whereas in Cymaprimadon the ridge connects to the protoco- nid and the basin is lingual to it. The relationship, if any, is distant. Tentatively, I believe that there is a relationship, but that the line leading to Solenodon separated 254 FIELDIANA: GEOLOGY, VOLUME 16 from the ancestral stock of the other two before they differentiated from each other. It seems improbable that venom, absent from all other mammal- lian groups, would develop absolutely independently in three fami- lies of Insectivora (Soricidae — Pearson, 1942; Solenodontidae — Rabb, 1959; Cymaprimadontidae — this publication). For this rea- son I tend to regard the three as somewhat more closely related to each other than they are to some other families of insectivores. The anatomy of the mandibular canal seems to be a solid line of evidence linking the Pantolestidae, Cymaprimadontidae, and Solenodontidae. The three would all fall, probably, within the suborder Sorico- morpha of the order Lipotyphla of Butler (1956) . They would occupy the same position in McDowell's (1958) classification, but the Pan- tolestidae and Cymaprimadontidae might properly be excluded from the superfamily Soricoidea. Van Valen's (1966) "group M" is stated on p. 104 to include the Pantolestidae and on p. 108 to be ancestral to the primates, which in turn are ancestral to the rodents; "group M" is also, apparently, ancestral to the lagomorphs. Since "group M" is not a formal taxonomic designation, it cannot be prop- erly considered. However, it seems very clear that the Cymapri- madontidae are related at an ordinal level to the Pantolestidae, and that they are not ordinally related to primates, rodents, or rabbits. REFERENCES Butler, P. M. 1956. The Skull of Ictops and the Classification of the Insectivora. Proc. Zool. Soc. London, ser. B, 126, pp. 453-481. Clark, John 1937. The stratigraphy and paleontology of the Chadron Formation in the Big Badlands of South Dakota. Ann. Carnegie Mus., 25, pp. 261-350. McDowell, S. B., Jr. 1958. The Greater Antillean insectivores. Bull. Am. Mus. Nat. Hist., 115, art. 3, pp. 117-214. Pearson, 0. P. 1942. On the cause and nature of a poisonous action produced by the bite of a shrew {Blarina brevicandata) . Jour. Mammal., 23, pp. 159-166. Rabb, G. B. 1959. Toxic salivary glands in the primitive insectivore Solenodon. Chgo. Acad. Sci., Nat. Hist. Miscellanea, No. 170, pp. 1-3. Van Valen, Leigh 1966. Deltatheridia, a new order of mammals. Bull. Am. Mus. Nat. Hist., 132, art. 1, pp. 1-126. K,