450
Journal of Paleontology 92(3):442–458 Genus Buenellus Blaker, 1988
Type species.—Buenellus higginsi Blaker, 1988 from the lower part of the Buen Formation, Peary Land, North Greenland, by original designation.
Other species.—Buenellus chilhoweensis n. sp. (see below).
Diagnosis.—(Emended from Babcock and Peel, 2007.) Prox- imal portion of posterior cephalic margin approximately trans- verse or weakly posterolaterally oriented when traced distally from axial furrow to adgenal angle; adgenal angle weak or absent so that base of genal spine lies slightly posterior to or opposite lateral margins of LO. Genal spine broad-based. Intergenal spine absent or reduced to small dorsal swelling on posterior cephalic border immediately distal to adgenal angle. Glabella slightly tapered anteriorly. SO deepest midway between sagittal line and axial furrow, extremely shallow or not incised adjacent to axial furrow. Cephalic border furrow, axial furrow, and glabellar furrows, especially those anterior to SO, very shallow. Short preglabellar field. Weak parafrontal band extends around lateral and anterior margins of LA. Ocular lobe narrow (tr.), anterior portion of more subdued relief than pos- terior portion, summit lower than LA and separated from it by break in slope; inner margin poorly defined from interocular area; posterior tip transversely opposite lateral margin of SO or L1. Interocular area slightly narrower to slightly wider (tr.) than width (tr.) of extraocular area opposite S1. Intergenal ridge and posterior ocular line converge at intergenal swelling. Fine granulations on external surface of exoskeleton. Thorax (only known from type species) of 17 or 18 segments, maintaining width or widening slightly backward to eighth segment, then tapering posteriorly. Pygidium simple; may bear one thoracic- like segment fused to anterior edge. Posterior margin of pleurae of first nine or ten segments sigmoidally curved. Pleural spines short (exsag.), tips opposite axial ring of next one or two segments.
Remarks.—Buenellus was previously only known with certainty from the type species in North Greenland (see Babcock and Peel, 2007, p. 404, for discussion of a supposed occurrence in Novaya Zemlya). Discovery of Buenellus chilhoweensis n. sp. demonstrates that the genus occupied both the Innuitian and Iapetan margins of Laurentia. The generic diagnosis is herein emended to accommodate Buenellus chilhoweensis n. sp. and expanded to include several previously unspecified features that distinguish Buenellus from similar taxa. Blaker and Peel (1997) discussed differences between
Buenellus and several other similar genera, including the nevadioids Nevadella and Nevadia, the possible nevadioid Limniphacos, the holmiid olenelloids Holmia Matthew, 1890 and Kjerulfia Kiaer, 1917, and the problematic Callavia Matthew, 1897, which has been variously considered a holmiid
(Palmer and Repina in Whittington et al., 1997; Jell and Adrain, 2003) or a judomioid (Lieberman, 2001). Buenellus also shares many features with Pseudojudomia egregia Egorova in Gorjansky et al., 1964, which is the type and only known species of Pseudojudomia, including details of the glabellar furrows, the nature of the contact between the ocular lobes and the anterior glabella, and a general cephalic effacement. Although it is possible that some of these shared features represent symplesiomorphies or homoplasies, it is likely that the two genera are closely related. (A formal hypothesis of their relationship will be presented in a forthcoming cladistic analysis [Webster, in preparation].) The two genera are most reliably distinguished by differences in the form of the posterior cephalic margin: in Pseudojudomia egregia the posterior cephalic margin arcs posterolaterally and uniformly curves into the inner margin of the genal spine so that the spine and the cephalic border are smoothly confluent; whereas in Buenellus the posterior cephalic margin is more transversely oriented (often with a slight anterior deflection at the adgenal angle) when traced abaxially and there is a more distinct (although certainly not sharply) curved geniculation marking where the genal spine contacts the posterior cephalic border. Other publications relevant to the diagnosis and validity of the genus Buenellus include: Blaker (1988, p. 34–35), Palmer and Repina (1993, p. 31), Blaker and Peel (1997, p. 50–52), Palmer and Repina in Whittington et al. (1997, p. 428), Jell and Adrain (2003, p. 353, 474), and Babcock and Peel (2007, p. 411–412).
Buenellus chilhoweensis new species Figure 4
1890 undetermined species of Olenellus; Walcott, p. 570.
1890 Olenellus thompsoni?; Walcott, table on p. 575 (eastern Tennessee occurrence).
1890 Olenellus, sp.?; Walcott, p. 583.
1891 species of Olenellus closely allied to Olenellus thompsoni and Olenellus asaphoides in that portion of the head preserved; Walcott, p. 154.
1895 trilobites; Keith, 1895, p. 3. 1933 olenellid trilobites; Resser, p. 746. 1936 olenellid trilobites; Grabau, p. 12. 1949 trilobites; King, p. 520. 1952 Olenellus; King et al., table 2 on p. 4. 1952 Olenellus sp.; King et al., p. 15. 1960 Olenellus; King and Ferguson, p. 36. 1965 Olenellus; Neuman and Nelson, p. D29. 2016 nevadiid trilobite; Hageman and Miller, p. 146, fig. 7d.
Holotype.—USNM 645831 (internal and external mold; Fig. 4.3, 4.4).
Figure 4. Buenellus chilhoweensis n. sp. from the Murray Shale, Chilhowee Mountain, Blount County, Tennessee, U.S.A. (1) Internal mold of cephalon from ICS-10567, USNM 633932; (2) internal mold of cephalon from ICS-10568, USNM 645832.; (3, 4) internal and external mold, respectively, of holotype cephalon from ICS-10567, USNM 645831; (5, 6) internal and external mold, respectively, of cephalon from ICS-10568, USNM 645833; (7) external mold of cephalon from ICS-10568, USNM 645834; (8) latex peel of external mold of incomplete cephalon found by Walcott in 1889 and mentioned by Walcott (1890, 1891), USNM 18446, dorsal view. (1–7) from upper part of Murray Shale, locality CM3; (8) from Little River Gap area (USNM Locality 17). Scale bars 5mm.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220
