Zhelestidae
Nessov et al. (1998) reviewed the complicated history of Late Cretaceous
Zhelestidae
classification, with the major complication arising from the nonassociation of incompletely known upper and lower dentitions of the included taxa.
Zhelestidae
have been reported from Middle Asia, Japan, North America, and Europe ( Archibald, 1996; Nessov et al., 1998; Setoguchi et al., 1999; Archibald et al., 2001; Kielan-Jaworowska et al., 2004; Archibald and Averianov, 2005) and in addition to dental elements are known from referred isolated petrosals ( Ekdale et al., 2004), tarsals ( Szalay and Sargis, 2006), humeri (Chester et al., 2007), and femora (Chester et al., 2008). Kielan-Jaworowska et al. (2004) recognized 10 genera: from Uzbekistan
Zhelestes
,
Sorlestes
(also known from Kazakhstan and Japan),
Aspanlestes
,
Parazhelestes
, and
Eoungulatum
; from North America
Alostera
,
Avitotherium
, and
Gallolestes
; and from Europe
Labes
and
Lainodon
. Archibald and Averianov (2005) included
Sorlestes
and
Eoungulatum
in
Zhelestes
and
Parazhelestes
, respectively, and are continuing to revise the Middle Asian taxa.
Zhelestidae
has been interpreted to be a paraphyletic stem lineage to placental ‘‘ungu- lates’’ within ‘‘Ungulatomorpha’’ ( Archibald, 1996; Nessov et al., 1998; Archibald et al., 2001; Kielan-Jaworowska et al., 2004) (fig. 31A). However, two of the principal proponents of this view recently have altered the allocation of zhelestids from ‘‘Ungulatomorpha’’ to Laurasiatheria (Archibald and Averianov, 2005; Averianov and Archibald, 2005), a broader grouping that includes cetartiodactyls, perissodactyls, carnivorans, pangolins, and bats. In contrast, the study by Wible et al. (2007), the most comprehensive analysis to date with regards to number of taxa and characters, identified zhelestids as stem placentals basal to cimolestids and asioryctitheres with no ties to placental ‘‘ungulates’’ or laurasiatherians (figs. 29, 30).
The monophyletic
Zhelestidae
identified by Wible et al. (figs. 29: H, 30) does not include one form,
Eozhelestes mangit Nessov, 1997
, from the early Cenomanian of Uzbekistan, thought to belong to this clade by Averianov and Archibald (2005). In contrast,
Eozhelestes
is united with
Paranyctoides
(see below).
Zhelestidae
is supported by five molar synapomorphies (figs. 33, 34; appendix 4: node H): M2 stylar shelf less than 25% total tooth width (character 65); M2 postmetacrista weak or absent (character 83); M2 conular region wide (greater than 0.51 total tooth length) (character 91); M2 protocone height subequal to paracone and metacone (character 96); and m2 hypoconulid close approximation to entoconid (character 120). Interestingly,
Eozhelestes
is unknown for the first four characters and has the zhelestid state for the fifth.
Within
Zhelestidae
,
Sheikhdzheilia
from the early Cenomanian of Uzbekistan (Averianov and Archibald, 2005) is the oldest as well as the basalmost form (fig. 30), confirming Averianov and Archibald’s (2005: 599) observation that it was ‘‘possibly the one retaining the greatest number of ancestral characters among known zhelestids.’’ Two monophyletic clades are identified: a North American clade with
Avitotherium
and
Gallolestes
; and an Uzbekistani clade with
Parazhelestes
,
Zhelestes
, and
Aspanlestes
. The former is support- ed by two molar synapomorphies (appendix 4: node H 3): M2 precingulum present (character 97; fig. 33) and m2 anterior and labial (mesiobuccal) cingular cuspule (f) present (character 114). The latter is supported by seven postcanine synapomorphies (appendix 4: node H 4): penultimate lower premolar with metaconid swelling (character 53); ultimate lower premolar paraconid indistinctive (character 55); M2 metastylar lobe labial relative to parastylar lobe (character 66; fig. 33); M2 preparastyle present (character 69; fig. 33); m2 protocristid transverse (character 113; fig. 34); m2 cristid obliqua attaching labial to notch in protocristid (character 116; fig. 34); and hypoconulid of ultimate lower molar short and erect (character 121). The phylogenetic analysis in Archibald et al. (2001), which did not include
Sheikhdzheilia
and
Lainodon
, identified a slightly different Middle Asian clade with
Aspanlestes
,
Zhelestes
, and
Parazhelestes
(including
Eoungulatum
) and the position of the North American taxa was unresolved (fig. 31B).
Maelestes
has few resemblances to zhelestids. One feature that is unique among Cretaceous eutherians to petrosals in
Maelestes
and to isolated petrosals attributed to Middle Asian zhelestids by Ekdale et al. (2004) is a short, horizontal prootic canal. Yet, these same forms differ in nearly every other petrosal character.
