Behemotops, Domning, Ray, and McKenna, 1986
|
publication ID |
https://doi.org/ 10.4202/app.00990.2022 |
|
persistent identifier |
https://treatment.plazi.org/id/E16A87B0-FF97-F25C-0C5C-FCBD7316FCFE |
|
treatment provided by |
Felipe |
|
scientific name |
Behemotops |
| status |
|
Behemotops cf. B. proteus Domning, Ray, and
McKenna, 1986 Fig. 2 View Fig .
Material.— LACM 124106, right lower postcanine teeth ( Ray et al. 1994) from LACM locality 5123, Disque Quadrangle, Washington, Pysht Formation, late Oligocene; RBCM.EH2007. 008.0001, a partial skull, including canine tusk and two molars, and 12 thoracic vertebrae, 17 ribs ( Beatty and Cockburn 2015) from Sombrio River in Juan De Fuca Provincial Park (Vancouver Island, Canada), from the late Oligocene Sooke Formation. RCBM EH2008 010 0001 ( Fig. 2 View Fig ) is a single cusp from an upper molar from near Kirby Creek (Vancouver Island, Canada), from the late Oligocene Sooke Formation.
Description.— RCBM EH2008 010 0001 is a single cusp from an almost desmostylodont tooth ( Fig. 2 View Fig ) that resembles the paracone of Behemotops proteus from Muir Creek ( RBCM. EH2007.008.0001; Beatty and Cockburn 2015). Desmostylodont teeth are those having columnar cusps made of thick enamel, which are considered to be traits of Paleoparadoxia , Cornwallius , and Desmostylus ( Clark 1991) . This cusp, in isolation, appears almost columnar, particularly because of its almost vertical edge. This is the feature that most resembles the paracone or metacone of the left M2 of B. proteus, RBCM. EH 2007.008.0001. The paracone and metacone of RBCM. EH2007.008.0001 and RCBM EH2008 010 0001 lack the cingulum that is otherwise characteristic of the postcanine teeth of B. proteus (Doming et al. 1986; Ray et al. 1994). The size of RCBM EH2008 010 0001 is also similar to the paracone or metacone of B. proteus . The cusp of RBCM EH2008 010 0001 is smaller than the equivalent cusps of C. sookensis , which also lack a cingulum, but are larger than this new specimen.
Family Desmostylidae Osborn, 1905
Genus Cornwallius Hay, 1923
Cornwallius sookensis ( Cornwall, 1922)
Figs. 3 View Fig , 4 View Fig .
Holotype: RBCM 486, a left lower molar.According to Cornwall (1922) the “type” is a tooth, the same specimen described by Lawrence M. Lambe in Kermode (1917); he also describes a second tooth found in 1921. Of these two teeth, RBCM 486 (a left lower molar) and RBCM 491 (a right M3), the former is the holotype ( Cornwall 1922: fig. 1A; Hay 1924: pl. 2: 1–3), and is most likely an m1 or m2 ( Beatty 2009).
Type locality: Cliffs between Coal (Kirby) and Muir creeks, Vancouver Island, British Columbia, Canada.
Type horizon: Sooke Formation, Zemorrian (late Oligocene).
Material.— RBCM 491, a right M3 ( Cornwall 1922: fig. 1B; Hay 1923: fig. 4; Hay 1924: textfig. 1, pl. 1: 4, 5, pl. 2: 4, 5) from Vancouver Island Sooke Formation, late Oligocene. UCMP 32682, a fragment of a lower molar including two cusps ( Clark and Arnold 1923: fig 3a, b; VanderHoof 1937) both of which were found from between Coal (Kirby) and Muir creeks, Vancouver Island, British Columbia, Canada; UCMP 36078, a right M1 and UCMP 36079, a right m2; from Bahia San Carlos, previously reported as San Telmo Point ( VanderHoof 1942), and Punta San Telmo, Baja California, Mexico ( VanderHoof 1942: pl. 1). USNM 157811, an isolated partial adult lower molar, comprising two straight, moderately hypsodont columnar cusps still partially embedded in matrix and including intercuspal matrix that appears to include remains of crushed shells ( Beatty 2009); USNM 181738, a nearly complete (edentulous) and only slightly laterally distorted skull of a small individual, which is most likely a subadult ( Beatty 2009); USNM 181739, an adult edentulous left mandibular ramus ( Beatty 2009); USNM 181740, skull of a large, presumably adult, individual with left and right C1, M2, M3 and additional roots of incisors and one M1 ( Reinhart 1982; Beatty 2009); USNM 181741, a right mandible with two molariform teeth, which are either m1 and m2, or m2 and m3, is much smaller than what would fit with the larger skull ( USNM 181740; Beatty 2009). USNM 181741 appears to have fit an animal the same size as that to which the smaller skull ( USNM 181738) belonged, and is probably a juvenile or subadult (like USNM 181738) ( Beatty 2009); USNM 181743, a heavily worn isolated lower premolar ( Beatty 2009); USNM 214737, a right pelvis, mostly complete except for portions of the sacroiliac joint and ischiopubic ramus ( Beatty 2009); USNM 214738, a tibial diaphysis ( Beatty 2009); USNM 214740, a partial adult mandible, including the symphysis and a portion of the left tusk ( Beatty 2009); USNM 244034, an edentulous left mandible from an individual of the same size as USNM 181741, possibly belonging to the same individual as they were found at the same spot in different years ( Beatty 2009); USNM 244036, a left M 2 in which the accessory cusp anterior to the protocone is broken off and partially restored with a waxy substance ( Beatty 2009); USNM 333334, an isolated partial lower molar comprising two straight cusps, mostly free of matrix, with only a small remnant of intercuspal matrix that appears to include the fossilized remains of plant material ( Beatty 2009). USNM 157811, 181738–181741, 181743, 214737, 214738, 214740, 244034, 244036, and 333334 are all from near Seal Rock State Park, Lincoln County, Oregon, USA ( Beatty 2009). Newly referred RBCM.EH2005.002.0001, a right M2 or M3 ( Fig. 3 View Fig ); CMN 9196, a right m1 ( Fig. 4 View Fig ) from near Kirby Creek (Vancouver Island, Canada), late Oligocene Sooke Formation.
Description.— RBCM.EH2005.002.0001: A right upper second or third molar that shows very little sign of wear and is missing its roots. This specimen is rather fragile and the broken edges where the roots were attached appear thin, suggesting that the roots were incompletely formed. The cusp arrangement, including accessory cusps and styles, are identical in size and position to those of the upper left molars of the large skull of Cornwallius sookensis USNM 181740 ( Beatty 2009). The cusps and styles of RBCM.EH2005.002.0001 are also identical to UCMP 36078 ( VanderHoof 1942), though the small accessory cusp/style between the paracone and metacone appears to be broken off in UCMP 36078, making its size uncertain. Additionally, another tooth, IGM 3688 from the El Cien Formation at Punta San Carlos, Baja California Sur ( Applegate 1986) resembles the m2 of USNM 181741 as well. It seems that RBCM.EH2005.002.0001 represents the same taxon as USNM 181740 from Oregon and UCMP 36078 and IGM 3688 from Baja California.
The wear on the mesial talon, paracone, protocone, and metacone all show a small exposure of dentine, whereas the wear on the hypocone has only formed a small facet with defined edges, but no dentine exposure. This is a more advanced stage of wear than the tooth of C. sookensis from Baja California Sur ( UCMP 36078) ( VanderHoof 1942). This resembles the wear seen on some partially erupted molars in subadult Desmostylus hesperus specimens ( USNM 8191, USNM 214743, UOMNHCH F79346).
CMN 9196 About CMN : This tooth is a right lower second or third molar Fig. 4 View Fig ), most similar in morphology to the teeth of the mandible referred to C. sookensis, USNM 181741 ( Beatty 2009) . USNM 181741 About USNM is a right mandible containing a very worn m1 and less worn m2. The m1 is worn to the point where the dentine lakes of the paraconids and metaconid are merged, as are the dentine lakes of the hypoconid and entoconid. The only cusp of the m1 remaining was the accessory cusp between the paraconids and hypoconid. This seems to be only because it was close enough to the base of the crown to retain its enamel edges and evade this dentine lake merger. The m2 of the same specimen, though at a similar stage of wear as CMN 9196 About CMN , notably lacks an accessory cusp between the paraconids and hypoconid like the m1 has. Thus , CMN 9196 About CMN is most likely a lower right m1 of an animal just like USNM 181741 About USNM ( Beatty 2009). As far as it is possible to tell from isolated teeth, this is most likely to be the same species, C. sookensis . Moreover , CMN 9196 About CMN is an almost mirror image of the holotype first or second molar ( RBCM 486 View Materials ). It is nearly at the same wear stage as RBCM 486 View Materials ( Beatty 2009: fig. 2) and may represent the same individual animal .
Remarks.— Despite its small size, the holotype ( RBCM 486) is virtually identical to the posterior molar of USNM 181741. USNM 181741 appears to have fit an animal the same size as that to which the smaller skull ( USNM 181738) belonged, and is probably a juvenile or subadult (like USNM 181738) ( Beatty 2009).
Stratigraphic and geographic range.—Zemorrian (upper Oligocene) of Vancouver Island, British Columbia ( Canada); Unalaska Island, Aleutian Islands, Alaska ( USA); Yaquina Bay and Beaver
Creek, Lincoln County, Oregon ( USA); and Bahia San Carlos, Baja California Sur ( Mexico).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
|
Kingdom |
|
|
Phylum |
|
|
Class |
|
|
Order |
|
|
Family |
Behemotops
| Beatty, Brian Lee 2023 |
Cornwallius
| Hay 1923 |
Desmostylidae
| Osborn 1905 |