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Systematic Descriptions
Class MAMMALIA
Order INSECTIVORA
Genus SOREX Linnaeus, 1758 (Long-tailed shrews)
Characters--Number of teeth: incisors, 4/2; canines, 1/0; premolars, 2/1; molars, 3/3 = 32. Size very small, ears hidden in the soft fur, eyes minute, muzzle pointed. These shrews are terrestrial in habit, living generally along the edges of marshes, swamps, and streams where the ground is moist. The genus is not known to be represented by species living in Kansas at the present time.
SOREX TAYLORI Hibbard (Taylor's shrew)
Sorex taylori HIBBARD, 1938, Kansas Acad. Sci. Trans., vol. 40, pp. 242-243, fig. 1. Type locality, Meade County, Kansas, Loc. no. 2, upper Pliocene.
Plate 1, figure 5
In the collection of fossils from the Borchers ranch are parts of five rami referable to this form. KUMVP no. 6118 is the posterior part of a right ramus bearing M1-M3. The anteroposterior diameter of the molar series is 3.3 mm. Specimen no. 5232 is the posterior part of a right ramus, bearing M1-M3; anteroposterior diameter of the molar series is 3.2 mm. Specimen no. 5233 possesses P4-M2. P4 is not as large as the P4 of the recent form, Sorex obscurus obscurus Merriam; it has a shorter anteroposterior diameter but a better-developed heel. The ramus is also more robust. The specimens agree well with the upper Pliocene species in that the hypoconid and entoconid of M3 are not as well developed as in S. obscurus obscurus, so that the heel is smaller than in that form. The coronoid process of the specimens also differs from that of the recent species and agrees well with that of the fossil form in that there is a better-developed depression on the labial side for the attachment of the muscle.
Order CARNIVORA
Genus MUSTELA Linnaeus, 1758 (Weasels)
Characters--Number of teeth: incisors, 3/3; canines, 1/1; premolars, 3/3; molars, 1/2 - 1 = 34 or 32. Small, long-bodied carnivores having short legs and feeding upon live prey, chiefly rodents and small birds.
MUSTELA Sp.
Plate 1, figure 3
Part of the left ramus (KUMVP no. 5750) of an adult specimen of a weasel intermediate in size between Mustela cicognanii cicognanii Bonaparte and Mitstela frenata noveboracensis (Emmons) was found. The trigonid of M1 is longer than the talonid; all evidence of M2 is lacking; the anteroposterior diameter of M1 is 4.8 mm; the transverse diameter of the tooth measured across the protoconid is 1.8 mm; the depth of the ramus below M, is 4.3 mm.
Genus SPILOGALE Gray, 1865 (Spotted skunks)
Characters--Number of teeth: incisors, 3/3; canines, 1/1; premolars, 3/3- molars, 1/2 = 34. A small spotted skunk, incorrectly called the "civet", "civet cat", or "pole cat."
SPILOGALE cf. LEUCOPARIA Merriam (Rio Grande spotted skunk)
Spilogale leucoparia MERRIAM, 1890, North American Fauna, no. 4, p. 11. Type locality, Mason, Mason County, Texas.
Plate 1, figures 1, 14
In the collection there are two right fragmentary rami bearing M1, which in all respects correspond to those of the recent form. M1 of KUMVP no. 5129 has an anteroposterior diameter of 6.7 mm. Ramus no. 6141 contains P4-M1; the anteroposterior diameter of the teeth is 9.7 mm; the anteroposterior diameter of M1 is 7.0 mm; the transverse diameter, measured across the protoconid-metaconid, is 3.1 mm; the depth of the ramus below the protoconid of M1 is 4.1 mm. Ramus no. 6117 possesses a narrower M1 than the other fossils, and M2 is slightly smaller than that in specimens of Spilogale leucoparia examined. The anteroposterior diameter of M1 and M2 is 9.3 mm; the anteroposterior diameter of M1 is 6.4 mm; the transverse diameter across the protoconid-metaconid is 2.25 mm; the depth of the ramus below the protoconid is 5.5 mm.
Plate 1 [A larger PDF version of this figure is available.]
Spilogale cf. leueoparia Merriam
1--Left ramus, P4-M1 (no. 6141), lateral and occlusal views, x4.
14--Left ramus, M1-M2 (no. 6117), lateral and occlusal views, x4.
Citellus meadensis, n. sp.
2--Right ramus, P4-M1 (no. 6169, holotype), occlusal view, x3.
7--Left maxillary, P4-M2 (no. 6119, paratype), occlusal view, x3.
Mustela sp.
3--Left ramus, M1 (no. 5750), lateral and occlusal views, x4.
Hypolagus sp.
4--Left P3 (no. 5735L), occlusal view, x6.
6--Right P3 (no. 5735h), occlusal view, x6.
Sorex taylori Hibbard
5--Right ramus, M1-M3 (no. 6118), lateral and occlusal views, x13.
Nekrolagus sp.
8--Right P3 (no. 6155), occlusal view, x6.
Perognathus pearlettensis, n. sp.
9--Right ramus, P4-M3 (no. 6127, holotype), lateral and occlusal views, x10.
12--Left maxillary, P4-M3 (no. 5362, paratype), occlusal view, x10.
Geomys sp.
10--Left ramus, P4-M2 (no. 5234), lateral and occlusal views, x3.
Zapits burti, n. sp.
11--Right M1-M3 (no. 6152, holotype), occlusal view, x10.
Citellus cragini, n. sp.
13--Left maxillary, M1-M3 (no. 6168, holotype), occlusal view, x3.
All specimens figured are in the collection of the University of Kansas
Museum of Vertebrate Paleontology.
Order RODENTIA
Genus CITELLUS Oken, 1816 (Ground squirrels)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 2/1; molars, 3/3 = 22. Squirrels living on the ground and making their home in burrows. Their claws are slightly curved and long, being adapted for digging.
CITELLUS MEADENSIS, n. sp. (Meade ground squirrel)
Plate 1, figures 2, 7
Type--KUMVP no. 6169, anterior part of right ramus of adult, bearing P4-M2. Paratype, no. 6119, fragmentary left maxillary bearing P4-M2.
Horizon and type locality--Pleistocene, Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This ground squirrel is nearly as large as Citellus mexicanus parvidens (Mearns). On P4 the protoconid and paraconid (Howell, North American Fauna, no. 56, pl. 12, 1938) are well developed and are separated by a deep sulcus or groove. The hypoconid is larger than that of Citellus tridecemlineatus arenicola Howell. The reentrant angle between the protoconid and hypoconid is wide, but does not extend as far across the crown of the tooth as in recent species. Between the protoconid and paraconid of M1 and M2 is a well-developed groove, in the center of which is a deep pit, the anterior border of which forms a prominent convexity on the anterior part of the molars. This is a greater convexity than exists in C. mexicanus parvidens. A similar process is found in some immature specimens of C. tridecemlineatus but is lost early in wear. The posterior border of the groove is partly closed by an enamel ridge that extends from the posterior border of the protoconid diagonally to the base of the paraconid. This condition is present in a vestigial stage in C. mexicanus parvidens, but has not been observed to be as well developed in any recent species.
Description of type--P4 has a transverse diameter of 1.8 mm, and an anteroposterior diameter of 1.7 mm; the anteroposterior diameter of the P4-M2 series is 5.85 mm; the transverse diameter of M1 is 2.0 mm; the transverse diameter of M2 is 2.3. The entoconid is better developed than that of recent forms.
Discussion--Citellus meadensis is distinguished from C. bensoni Gidley, C. tuitus Hay, C. cochisei Gidley, and C. taylori Hay by its smaller size, and from the small Citellus from the upper Pliocene of Kansas by the narrower transverse diameter of its molars and by the development of the pit in the groove between the protoconid and paraconid of the molars, as well as by the pronounced ridge extending from the posterior border of the protoconid to the posterior base of the paraconid.
CITELLUS CRAGINI, n. sp. (Cragin ground squirrel)
Plate 1, figure 13
Type--KUMVP no. 6168, part of left maxillary bearing M1-M3.
Horizon and type locality--Pleistocene, Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This ground squirrel is larger than Citellus franklinii (Sabine). The protoloph and melaloph are well developed on M1 and M2, and join the protocone. M3 has only a protoloph, the metacone is low and is separated from the protocone by a sulcus and an enamel fold.
Description of type--The anteroposterior diameter of M1-M3 is 9.1 mm. M1 and M2 have a transverse diameter greater than the anteroposterior diameter. The transverse diameter of M3 equals its anteroposterior diameter. The parastyle of M1 and M2 is developed as in C. columbianus columbianus (Ord), but the metastyle is better developed. M3 resembles that of C. columbianus columbianus more than that of other recent forms examined, although the parastyle is higher lingually and joins the protocone near the top of the crown. The protocone inflection of the enamel in the region of the metaloph is larger in the fossil form, and is well separated from the protoloph by a broad deep groove. Labiad to the enamel inflection and separated from it by a sulcus is a well developed metacone. The size and character of M3 distinguishes Citellus cragini from other fossil and recent forms.
This species is named for F.W. Cragin who collected the first vertebrate fossils from this area and also reported on the geological formation.
Genus GEOMYS Rafinesque, 1817 (Eastern pocket gophers)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 1/1; molars, 3/3 = 20. Fossorial, short-tailed rodents having long curved claws on forefeet for digging, large external cheek pockets, small eyes, vestigial ears, nearly hidden under short fur, and incisors having two grooves on outer surface.
GEOMYS Sp.
Plate 1, figure 10
Numerous isolated gopher teeth and fragmentary rami bearing P4 and M1 occur in the Borchers collection. These are seemingly from immature specimens, for they are small. A few isolated teeth as large as those of adult Geomys lutescens (Merriam) have been found. The enamel pattern of P4 is that of typical Geomys. Specimen no. 5234 possesses P4-M2; the anteroposterior diameter of the series is 5.0 mm; the anteroposterior diameter of P4, is 2.6 mm; the greatest transverse diameter is 2.0 mm; the transverse diameter of the incisor is 2.1 mm.
Genus PEROGNATHUS Wied, 1839 (Pocket mice)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 1/1; molars, 3,/3 = 20. Small, terrestrial, long-tailed mice having grooved upper incisors and fur-lined external cheek pockets.
PEROGNATHUS PEARLETTENSIS, n. sp. (Pearlette pocket mouse)
Plate 1, figures 9, 12; Plate 2, figures 10, 14
Type--KUMVP no. 6127, nearly complete right ramus bearing incisor and P4-M3. Paratypes, no. 5231, fragmentary right ramus bearing P4-M3; no. 5354, fragmentary left ramus bearing P4-M3; no. 5353, fragmentary left ramus bearing incisor and P4 and M2; no. 5365, fragmentary left ramus bearing incisor and P4 and M2; no. 5709, fragmentary right ramus bearing P4 and M1; nos. 6146 and 6122, nearly complete right rami bearing incisor and P4; maxillary no. 5361, bearing P4-M2; and maxillary no. 5362, bearing P4-M3.
Horizon and type locality--Pleistocene, Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This pocket mouse is nearly as large as Perognathus apache Merriam, but possesses a shorter and more robust diastemal region and a shorter and broader condyloid process.
Description of type--The ramus is that of a young adult. The P4 is just wearing into an H pattern. The anteroposterior diameter of the molar series is 3.1 mm; the depth of the ramus on the labial side below P4 is 2.6 mm; the depth of the ramus on the labial side below M2 is 2.25 mm. The masseteric ridge is well developed but does not extend upward as near the dorsal surface of the diastemal region as in Perognathus flavus Baird. The anteroposterior diameter of P4 equals that of M3, but the transverse diameter is not as great. M1 is the largest tooth, M2 is second in size, and M3 is slightly larger than P4.
The paratypes agree in every respect with the type. They exhibit all stages of dentitional wear. The anteroposterior diameter of the molar series of nos. 5231 and 5709 is 3.0 mm. No. 5365 is a nearly complete ramus including P4. The anteroposterior diameter of the tooth is 0.65 mm; the anteroposterior diameter of the alveolar series, measured from the anterior root of P4 is 3.1 mm; the depth of the ramus on the outside, measured at P4, is 2.5 mm; the depth of the ramus measured on the outside below M2 is 2.2 mm. The mandibular foramen is located nearer the tip of the condyloid process than it is in Perognathus apache Merriam. Maxillary no. 5361 is that of a young adult. The anteroposterior diameter of P4-M2 is 2.4 mm. No. 5362 is that of an adult and bears P4-M3. The labial side of M2 and the anterior border of M3 are slightly chipped. The anteroposterior diameter of the molar series is 3.0 mm.
Perognathus pearlettensis is distinguished from the following recent High Plains species, Perognathus fasciatus Wied, P. flavescens (Merriam), and P. flavus Baird, by its slightly larger size, heavier incisor, more robust and shorter diastemal region of ramus, greater depth of ramus below the posterior border of M2, and a more robust condyloid process. Perognathus flavescens and P. flavus now inhabit the region in which the fossil species was collected.
The species is named for the "Pearlette ash" bed, from which the specimens were taken.
Genus ONYCHOMYS Baird, 1857 (Grasshopper mice)
Characters--Number of teeth: incisors, 1/1; canines,, 0/0; premolars, 0/0; molars, 3/3 = 16. A short-tailed mouse, the tail sparsely haired, nearly naked and tapering. Nocturnal in habit, living in burrows generally around clumps of "prickly pear" or sagebrush.
ONYCHOMYS FOSSILIS, n. sp. (Fossil grasshopper mouse)
Plate 2, figures 2, 6, 8
Type--KUMVP no. 5238, nearly complete left ramus bearing M1-M3. Paratypes, nos. 5237, 5239, 5255, 5258, 5259, 5319, 5721, 6154 to 6164, inclusive, are incomplete rami bearing M1-M3.
Horizon and type locality--Pleistocene., Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This "grasshopper mouse" the size of Onychomys leucogaster arcticeps (Rhoads) differs from that form in that the ramus is slightly lighter, M3 is larger, and the capsular process for the reception of the base of the incisor is not as pronounced and is not separated from the coronoid process by a deep groove.
Description of type--The ramus is that of an adult specimen. The anteroposterior diameter of M1-M3 at the crown is 4.4 mm; the depth of the ramus on the inner side below M3 is 2.5 mm. The basin between M3 and the ascending ramus is not developed as in Onychomys leucogaster arcticeps, being even shallower than in O. torridus torridus (Coues). The capsular process for the reception of the incisor is not as well developed as it is in O. leucogaster arcticeps and the groove between it and the coronoid process is not as deep as in the recent form. The capsular process is nearly as reduced as in O. torridus torridus. The mandibular foramen is developed as in O. leucogaster arcticeps, though larger. The mental foramen has approximately the size and position of that in O. leucogaster arcticeps, although the diastemal region of the jaw is not as robust. The paratypes agree with the type in characters mentioned, although they differ in anteroposterior length of crown series. The average length of the lower molar series including that of the type is 4.47 mm; extremes are 4.2 mm (an old adult) and 4.7 mm. The average depth below M1, measured on the inside of the ramus, of 8 specimens, is 3.7 mm. In the collection there are 169 rami and maxillaries bearing one or two molars, besides numerous rami and isolated teeth referable to this form.
Onychomys fossilis is distinguished from O. bensoni Gidley by its larger size, and from O. pedroensis Gidley by the following characters, which were listed by C.L. Gazin in a letter of March 20, 1941, after be had compared the Borchers form with the Curtis ranch specimen:
The capsular process for the reception of the base of the incisor and the groove separating the process from the rest of the ramus is better developed in Onychomys pedroensis than in your fossil. In O. pedroensis it is more like that in O. leucogaster arcticeps, however, of the several jaws representing the Curtis ranch form, only one has this portion preserved. Your form is distinct from O. pedroensis also in that the jaws of the Meade County form are not so robust, having a shallower and more slender jaw with narrower teeth. Your form is similar to O. pedroensis in that the last cheek tooth is less reduced and the masseteric crest extends farther forward than in the modern material.
Genus REITHRODONTOMYS Giglioli, 1874 (American harvest mice)
Characters--Number of teeth: incisors, 1/1; canines. 0/0; premolars, 0/0; molars, 3/3 = 16. The smallest of Recent Kansas mice, lacking cheek pouches; upper incisors possess longitudinal grooves; terrestrial in habit.
REITHRODONTOMYS PRATINCOLA, n. sp. (Meadow harvest mouse)
Plate 2, figure 7
Type--KUMVP no. 6167, part of right ramus bearing incisor and M1.
Horizon and type locality--Pleistocene, Loc. no. 91, Meade County, Kansas, Borchers fauna.
Diagnosis--This harvest mouse is smaller than Reithrodontomys albescens griseus (Bailey), and is distinguished by having a more acute angle between M3 and the coronoid process.
Description of type--M1 has an anteroposterior diameter of 1.2 mm. It is approximately the size of M1 in Baiomys taylori (Thomas) although it has a greater transverse diameter across the posterior part and has a narrower anterior lobe. The incisor is as robust as in Reithrodontomys and is strongly convex on the outer side, not flattened as in Baiomys. The angle between the alveolus of M3 and the ascending ramus is much narrower and more acute than in Reithrodontomys albescens griseus; in Baiomys there is a broad angle between M3 and the coronoid process. Reithrodontomys pratincola is distinguished from Reithrodontomys simplicidens Brown from the Conard Fissure deposit by its much smaller size.
Genus SIGMODON Say and Ord, 1825 (Cotton rats)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 0/0; molars, 3/3 = 16. A field rat of medium size, brown in color, terrestrial in habit living in meadows, in abandoned fields, and along fence rows. M3 has an S pattern.
SIGMODON HILLI n. sp. (Hill cotton rat)
Plate 2, figures 5, 12, 13
Type--KUMVP no. 5431, part of right ramus bearing incisor, M1-M3. Paratypes, nos. 5236, 5372, 5375-5378, 5396, 5400, 5402, 5403, 5406, 5408, 5410, 5421, 5423, 5424, 5468, 5612, 5686, 5691, 5759, all incomplete rami containing M1-M3; and nos. 5219 and 5475, left maxillaries containing M1-M3.
Horizon and type locality--Pleistocene, Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This species is slightly smaller than Sigmodon intermedius Hibbard. Molars are shorter in transverse diameter in comparison to their anteroposterior diameter than in other fossil and living species. The reentrant valleys are not as broad as in S. intermedius nor as constricted as in the recent species.
Description of type--The ramus is that of an adult specimen. The anteroposterior diameter of the crown series of M1-M3 is 5.25 mm; the greatest depth of the ramus is 5.2 mm; the depth of the ramus below M3 is 2.9 mm; the distance from the alveolus of M1 to the posterior border of the incisor alveolus is 3.0 mm. The mental foramen is not as close to the anterior root of M1 as in Sigmodon intermedius, approaching more nearly the condition found in S. ochrognathus Bailey. The reentrant angles or valleys are broader than in recent species, though not as broad as in S. intermedius. The anterior external reentrant valley of M1 closes off at a much earlier stage of wear than in S. intermedius. The transverse diameter of the molars is much smaller in proportion to the anteroposterior diameter of the tooth than it is in recent species. The anterior external reentrant valley of M1 is broad and well developed and persists much longer than in recent forms examined, although it is not as well developed as in 3. M3 possesses a small posterior loph, which gives the tooth a triangular outline in comparison to the M3 of recent forms. The anterior loop of M1 has a much smaller transverse diameter than that of recent forms and is not as compressed. The reentrant valleys of the upper molars are broader than in recent forms. The average length of the lower tooth series of 24 rami including the type is 5.21 mm; extremes are 4.8 mm (an immature specimen), and 5.5 mm. The maxillary tooth row of the two maxillaries measured 4.6 and 4.7 mm. The paratypes agree with the type and are individuals ranging from young adults to old adults. There were also collected 123 other rami and fragmentary maxillaries containing one or two molars, besides numerous isolated molars and rami without teeth.
This species is named for Dr. John Eric Hill, with whom I have spent many pleasant days collecting mammals.
Comparison--Sigmodon hilli is distinguished from Sigmodon curtisi Gidley by its smaller size and from Sigmodon minor Gidley by its slightly larger size and by the fact that the reentrant valleys of the upper molars are more oblique. Gidley (1922, p. 126) states, "the external reentrant valleys of the molars (as shown by specimen no. 10513, USNM) are of the normal modern type." In recent forms examined the external reentrant valleys are more curved and do not enter the crown in a straight oblique valley as in the fossil form. S. hilli is distinguished from S. medius Gidley in that the anterior internal reentrant valley is equal in length to the opposing outer valley, a character it has in common with S. intermedius. It is also distinguished by the lack of any evidence of a reentrant notch on the inner side opposite the posterior reentrant valley of M3. This is also a character not found in S. intermedius. In S. intermedius there occur small accessory cusps, an outgrowth of the cingulum, in the external posterior reentrant valleys of M1 and M2. There is no evidence of the accessory cusps in S. hilli.
Genus SYNAPTOMYS Baird, 1857 (Bog lemmings)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 0/0; molars, 3/3 = 16. A short-tailed mouse much like Microtus, the meadow mouse; upper incisors possess longitudinal groove; terrestrial and fossorial in habit.
SYNAPTOMYS (MICTOMYS) cf. VETUS Wilson. (Old lemming mouse)
Synaptomys vetus WILSON, 1933, Carnegie Inst. Wash., Publ. no. 440, pp. 124-126, figs. 2 and 3.
Plate 2, figures 1, 3, 4, 11
Material--Fragmentary left ramus (no. 6151) bearing M1 and M2; ten isolated upper and lower molars from Loc. no. 9, Meade County, Kansas, Borchers fauna.
Remarks--M1 consists of a posterior loop, three alternating triangles, and a closed anterior loop. The first and second triangles are confluent, the third closed. M1 corresponds to the M1 figured by Wilson (1933, pp. 124-126, figs. 2 and 3). M2 consists of an anterior loop, an alternating triangle, and a posterior loop. The anteroposterior diameter of M1 is 3.1 mm; the transverse diameter, 1.4 mm; the anteroposterior diameter of M2, 2.1 mm; the transverse diameter, 1.2 mm. M1 consists of an anterior loop and four closed alternating triangles. M1 differs from that figured by Wilson in that the anterior loop is larger than the closed alternating triangles. M2 consists of an anterior loop and three tightly closed alternating triangles. The teeth differ from those of Synaptomys vetus from the Grand View fauna in that the triangles are more tightly closed and are slightly larger.
Genus ZAPUS Coues, 1876 (Jumping mice)
Characters--Number of teeth: incisors, 1/1; canines, 0/0; premolars, 1/0; molars, 3/3 = 18. A mouse having elongated hind legs for jumping, very long tail, body the size of the white-footed field mouse; terrestrial in habit, living in meadows.
ZAPUS BURTI, n. sp. (Burt jumping mouse)
Plate 1, figure 11
Type--KUMVP no. 6152, incomplete right ramus bearing M1, M2, and M3. Paratype, no. 5341, fragmentary right ramus bearing M1 and the posterior part of M2, of an old adult.
Horizon and type locality--Pleistocene, Loc. no. 9, Meade County, Kansas, Borchers fauna.
Diagnosis--This form is approximately the size of Zapits hudsonius campestris Preble. The molars have more brachydont and slightly broader crowns. The enamel fold is not as crowded as in recent species of Zapus and Napaeozapus, although the tooth pattern is that of Zapus and Napaeozapus and not of Eozapus. M3 is reduced as in Zapus and is not as large as in Napaeozapus.
Description of type--The incomplete right ramus bears M1-M3. The anteroposterior diameter of the molar series at the crown is 3.8 mm. The crown pattern is that of a young adult. M1 possesses an anterior cusp that is separated from the rest of the tooth by a deep groove, The cusp possesses a well-developed dentine lake much larger than any observed in recent species in any stage of wear. The posterior external fold is broad and shallow and does not extend across the crown to the lingual side, but is separated from the lingual side by a deep enamel lake. The first posterior lingual enamel fold has been lost. The second and third lingual enamel folds are deeper, broader, and more complicated than in recent species of comparable age wear. The anterior lingual enamel fold is confluent with the anterior labial enamel fold, thus producing an isolated anterior cusp. The labial enamel folds of M2 are broader than those in the recent species. The posterior labial fold has not fused with the first posterior lingual fold to produce the long outer reentrant fold that is common in recent forms. In this respect the pattern of M2 resembles much the condition in Eozapus. There are three well-developed lingual folds. The posterior fold is beginning to cut off owing to wear to form a deep enamel lake. The anterior fold is complicated, possessing a small accessory cusplet, which is developed from the cingulum and which would eventually close the reentrant opening as the crown wore down. M3 is as small as in the recent species of Zapus. Its pattern corresponds more nearly with that of the recent forms than do the patterns of M1 and M2. The external enamel border of the tooth is missing, so the labial reentrant fold is destroyed. The paratype agrees with the type in size and tooth characters. The crown pattern is that of an old adult. Most of the internal reintrant angles have been cut off to form isolated lakes.
This species is named for Dr. W.H. Burt, to whom I am indebted for unlimited help in my study of recent mammals.
Zapus burti differs from Pliozapus solus Wilson in that M2 is not as broad; the dental pattern is more similar to that characteristic of the recent species of Zapus than of the fossil form.
Plate 2 [A larger PDF version of this figure is available.]
Synaptomys cf. vetus Wilson
1--Right M1 (no. 6151a), occlusal view, x6.
3--Left M1-M3 (no. 6151c), occlusal view, x6.
4--Right M1 (no. 6151b), occlusal view, x6.
11--Right M2 (no. 6151d), occlusal view, x6.
Onychomys fossilis, n. sp.
2--Left ramus, M1-M3 (no. 5238, holotype), lateral and occlusal views, x8. (Drawn by Walter Yost).
6--Right M1-M3 (no. 5239, paratype), occlusal view, x10.
8--Left M1-M3 (no. 5237, paratype), occlusal view, x10.
Sigmodon hilli, n. sp.
5--Left maxillary, M1-M3 (no. 5219, paratype), occlusal view, x10.
12--Right ramus, M1-M3 (no. 5431, holotype), lateral and occlusal views, X10.
13--Left ramus, M1-M3 (no. 5423, paratype), occlusal view, x10.
Reithrodontomys pratincola, n. sp.
7--Right ramus, M1 (no. 6167, holotype) lateral and occlusal views, x10.
Lepus cf. californicus Gray
9--Right P3-M1 (no. 5972), occlusal view, x6. Perognathus pearlettensis, n. sp.
10--Right ramus, P4-M3 (no. 5231, paratype), occlusal view, x10.
14--Right maxillary, P4-M2 (no. 5361, paratype), occlusal view, x10.
All specimens figured are in the collection of the University of Kansas
Museum of Vertebrate Paleontology.
Order LAGOMORPHA
Genus NEKROLAGUS Hibbard, 1939 (Extinct hare)
Characters--Number of teeth: incisors, 2/1; canines, 0/0; premolars, 3/2; molars, 3/3 = 28. P3 has anterior reentrant angles, and two external reentrant angles. The posterior external reentrant angle extends slightly more than half way across the crown of the tooth and is crenulated on the posterior border. Between the posterior external reentrant angle and the enamel of the lingual side of P3 is a well-developed enamel island, which is the top of a column extending the entire length of the tooth, separated from the lingual enamel border by a tract of dentine.
NEKROLAGUS Sp.
Plate 1, figure 8
In the collection are isolated rabbit teeth numbering more than a hundred, which were recovered by screening. One is a right P3 (no. 6155) of a young specimen referable to the genus Nekrolagus, previously known only from the Rexroad fauna, upper Pliocene, Meade County, Kansas.
Genus HYPOLAGUS Dice, 1917 (Under hares)
Characters--Number of teeth: incisors, 2/1; canines, 0/0; premolars, 3/2; molars, 3/3 = 28. P3 has two external reiintrant angles, neither of which extends more than three fourths the way across the tooth. The posterior angle is much deeper than the anterior. There are no anterior or inner reentrant angles on the surface of the tooth.
HYPOLAGUS Sp.
Plate 1, figures 4, 6
Two P3 (no. 5735), a left and a right belonging to young specimens, were collected. They differ from the upper Pliocene Hypolagus from Kansas in that the external reentrant angle extends slightly farther across the crown and is curved toward the anterior border of the tooth.
Genus LEPUS Linnaeus, 1758 (Hares, jack rabbits)
Characters--Number of teeth: incisors, 2/1; canines, 0/0; premolars, 3/2; molars, 3/3 = 28. P3 has two external reentrant angles, the posterior angle extending across crown of tooth to the lingual enamel border, also external anterior reentrant angles; terrestrial in habit, living in the open country.
LEPUS cf. CALIFORNICUS Gray
Lepus californicus GRAY, 1837, Charlesworth's Mag. Nat. Hist., vol. 1, p. 586.
Plate 2, figure 9
A fragmentary right ramus (no. 5972) bearing P3-M1 is referred to this species. The shape and depth of the ramus, and the position of the mental foramen are similar to those observed in recent specimens of Lepus c. melanotis (Mearns) from Kansas, with which it was compared. The only noticeable difference is the strongly crenulated reentrant angles of P4 and M1, which are more numerous and better developed than in the species L. californicus. The anteroposterior diameter of the crown of P3-M1 is 9.9 mm; the depth of ramus below P3, 14.9 mm; the distance of the mental foramen from the anterior alveolar border of P3, 15.7 mm.
Order ARTIODACTYLA
Genus CAMELOPS Leidy, 1854 (Camels)
Characters--Number of teeth: incisors, 1/3; canines, 1/1; premolars, 2/1-2; molars, 3/3. In upper molars the anteroposterior diameter is much greater than the transverse diameter. Extinct.
CAMELOPS sp.
There have been found associated with the other fossils two camel astragali (no. 4808) seemingly of the same individual. They correspond with those of Camelops, although they are larger and more robust than those of C. kansanus Leidy of the Cragin Quarry fauna, which were taken from a younger interglacial Pleistocene deposit.
Family ANTILOCAPRIDAE (Pronghorns)
A digit, astragalus, and a few well-worn isolated premolars of a small antelope have been found. On the basis of the material collected it is impossible to assign them to any particular genus.
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Kansas Geological Survey, Geology
Placed on web June 15, 2007; originally published July 1941.
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