New avian remains from the Eocene of Mongolia and the phylogenetic position of the Eogruidae (Aves, Gruoidea)

2005·2.8 MB·English

by  Clarke, Julia A

AMERICAN MUSEUM
Novitates
PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3494, 17 pp., 10 figures, 1 table November 29, 2005
New Avian Remains from the Eocene of Mongolia
and the Phylogenetic Position of the Eogruidae
(Aves, Gruoidea)
JULIA A. CLARKE,’ MARK A. NORELL,?
AND DEMBERELYIN DASHZEVEG?
ABSTRACT
A well-preserved nearly complete avian tarsometatarsus was collected by the 2002 expe-
dition of the Mongolian Academy of Sciences from upper Eocene deposits exposed at the
locality of Alag Tsav in the Eastern Gobi desert (Dornogov Aimag) of Mongolia. The new
specimen is identified as part of a proposed Eogruidae clade, although it is unclear whether it
is appropriately the holotype of a new species within this clade or referable to a previously
named species. The clade Eogruidae has, as its current contents, species named as part of the
traditional families Eogruidae + Ergilornithidae, which include several taxa of completely
didactylous and apparently flightless birds. Referral of the new fossil to the clade Eogruidae
is on the basis of derived reduction/loss of the metatarsal II trochlea.
A series of phylogenetic analyses was used to investigate the systematic position of Eogrui-
dae (including the new fossil, IGM 100/1447), which have been proposed to be a dominant
part of Eocene to Miocene Asian faunas. First, the Mayr and Clarke (2003) dataset for crown
clade Aves was used to investigate placement of Eogruidae within Aves, using a more com-
pletely known eogruid, Eogrus aeola, as an exemplar taxon. Eogrus aeola was identical to
the new tarsometatarsus for all scored characters. A strict consensus cladogram of three most
parsimonious trees from 1000 replicate heuristic searches placed Eogrus aeola in an unre-
solved polytomy with Psophiidae and Gruidae (Trumpeters and Cranes).
‘North Carolina State University, Department of Marine, Earth, and Atmospheric Sciences, Campus Box 8208,
Raleigh, NC 27695-8208 and North Carolina Museum of Natural Sciences ([email protected]); Division of
Paleontology, American Museum of Natural History.
? Division of Paleontology, American Museum of Natural History ([email protected]).
3 Division of Paleontology, American Museum of Natural History; Geological Institute of the Mongolian Academy
of Sciences, Ulaan Baatar, Mongolia.
Copyright © American Museum of Natural History 2005 ISSN 0003-0082
2. AMERICAN MUSEUM NOVITATES NO. 3494
Given the results of this analysis, Eogruidae (including IGM 100/1447) was analyzed in the
suborder Grues dataset of Livezey (1998). Eogruidae was placed as the sister taxon to an
Aramidae + Gruidae clade in the strict consensus cladogram of the eight most parsimonious
trees resulting from a branch and bound search. Because monophyly of the traditional order
Gruiformes has been repeatedly questioned, and the outgroups used in the original Grues
dataset were identified through analyses assuming monophyly, the impact of removing these
assumptions was investigated. Placement was robust to both changing outgroup assumptions
and to swapping in the more incompletely known IGM 100/1447 as an exemplar for Eogruidae.
INTRODUCTION Zhai, 1987). However, the location of the
Alag Tsav indicated in the present paper (fig.
New fossil remains, including that de-
1) is significantly different from this earlier
scribed here, were collected in 2002 from up-
work and is considered more accurate (Dash-
per Eocene deposits exposed at the locality
zeveg, personal commun.). Alag Tsav was
of Alag Tsav in the eastern Gobi desert (Dor-
discovered by D. Dashzeveg in 1982 (Dash-
nogov Aimag) of Mongolia (fig. 1) by an ex-
pedition of the Mongolian Academy of Sci- zeveg, 1985).
ences led by D. Dashzeveg. Alag Tsav (al- A well-preserved, nearly complete avian
ternative spelling: Alag Tsab, Dashzeveg, tarsometatarsus (IGM 100/1447; fig. 2) was
1996a, 1996b) is located close to the Chinese found in a light grey sandstone in the main
border just southeast of the well-known Pa- exposures of Alag Tsav, where it was asso-
leogene Ergilin-Dzo locality and 30 kilome- ciated with remains of Ardynomys russelli
ters south of the center of Ulaan Badrakh (Dashzeveg, 1996a). In addition to Ardyno-
Sum (Dashzeveg, 1985; Russell and Zhai, mys russelli (Cylindrodontidae), Hyaenodon
1987). The approximate coordinates of the (Hyaenodontidae), Gigantamynodon (Amy-
locality were previously given as latitutde nodontidae), Stenoplesictis (Viverridae), Te-
38°29'N; longitude 125°49’'E; (Russell and leolophus (Deperetellidae), and the basal ru-
COO
a
Ulaanbadrakh ~
o . > SyG o =
CA
© ‘Alag Tsav oS ere”
Bis eQ' Oo Khoer Dzan
Bl
GO
Bajan Tsav Ergil Obo 7ER N
e e EAS
Ergilin Dzo BA s iN
9 eo
MONGOLIA
Shara Murun
Region
area of
detail
Fig. 1. Map of the Paleogene bird localities in the eastern Gobi Desert, Mongolia, including Alag
Tsav, where the new fossil was recovered.
2005 CLARKE ET AL.: EOCENE AVIAN FROM MONGOLIA 3
Fig. 2. The right tarsometatarsus IGM 100/1447 in (A) plantar, (B) lateral, (C) dorsal, (D) medial,
(E) proximal and (F) distal views. Anatomical abbreviations: he hypotarsal canal, fs flexor sulcus, Ipe
lateral plantar crest, pvf proximal vascular foramen, tct m. tibialis cranialis tubercles.
+ AMERICAN MUSEUM NOVITATES NO. 3494
minant Archaeomeryx are also known from IIl:1 have also been identified (Wetmore,
these deposits (Dashzeveg, 1985, 1996b; Rus- 1934; Kurochkin, 1976, 1981).
sell and Zhai, 1987). The Sevkhul Member Wetmore (1934) originally named the fam-
(Ergilin Dzo Formation) has been correlated ily Eogruidae for the species Eogrus aeola.
with deposits overlying the avian fossil bear- All of the remains that he referred to this
ing unit at Alag Tsav (Dashzeveg, 1996b: fig. species, and including those illustrated in this
1). Therefore, this unit must be older than the paper (figs. 3-7, 8B), were from localities in
fossil-bearing units at the classic eastern Gobi the Shara Murun region, China (fig. 1), and
localities of Ergilin Dzo and Khoer Dzan (fig. from deposits assessed to be middle Eocene
1), where the Sevkhul and overlying Ergilin in age (Ulan Shireh/Irdin Manha Formations;
Members of the Ergilin Dzo Formation (Rus- Russell and Zhai, 1987). These localities in-
sell and Zhai, 1987) are exposed. clude Chimney Butte, Camp Margetts, (e.g.,
The boundary between the Eocene and Ol- AMNH 2946; figs. 6B, 7) and sublocalities
igocene in the section at Ergilin Dzo and southwest of Iren Dabasu. One specimen
Khoer Dzan has been interpreted to lie below (AMNH 2947) was collected north of Ar-
the Ergilin Member (Ergilin Dzo Formation; shanto Obo (Wetmore, 1934) and is also of
Dashzeveg, 1996b). It is in the Ergilin Mem- middle Eocene age (Russell and Zhai, 1987)
ber that early Oligocene genera of mammals but from the Arshanto Formation (Radinsky,
are first observed (e.g., Bothriodon, Entelo- 1964).
don, Ronzotherium; Dashzeveg 1996b; Rus- Wetmore (1934) also discussed material
sell and Zhai, 1987). The relationship of this identified as Eogrus sp. collected in Mon-
boundary to intercontinental faunal correla- golia near “‘Ardyn Obo”’ (i.e., Ergil Obo =
tions and the Eocene/Oligocene boundary in sublocality of Ergilin Dzo, Ergilin Member,
Europe and North America has been exten- Ergilin Dzo Formation; early Oligocene,
sively discussed in Dashzeveg and Devyatkin Russell and Zhai, 1987; fig. 1, this paper) and
(1986) and Dashzeveg (1993, 1996b). Fur- the Tunggur Formation exposed near Wolf
thermore, based on comparisons with well- Camp 40 miles southeast of Iren Dabasu,
known faunas from deposits in Inner Mon- Shara Murun region (middle Miocene; Wang
golia, China, the exposures at Alag Tsav are et al., 2003). One of these specimens
interpreted as contemporaneous with the (AMNH 2949; fig. 8A), from the Tunggur
Shara Murun Formation exposed at Ulan Usu Formation, originally considered to be from
(Dashzeveg, 1985, 1991), assessed to be late a distinct taxon closely allied with Eogrus
Eocene in age (Russell and Zhai, 1987). Alag aeola if not part of the same species (Wet-
Tsav is one of the few localities in Mongolia more, 1934: 12), was later indicated as the
interpreted to represent this part of the Eo- holotype specimen of a new species. This
cene (Russell and Zhai, 1987). species, Eogrus wetmorei, named in a foot-
Avian fossils are comparatively abundant note in Brodkorb (1967), was diagnosed by
from the Late Eocene and Early Oligocene its being slightly smaller than Eogrus aeola.
of the eastern Gobi Desert, where they have Subsequently, three additional species were
been recovered primarily from Khor Dzan named and placed in the Eogruidae: Eogrus
and Ergilin Dzo in Mongolia and from the crudus (Kurochkin, 1981) from middle upper
Shara Murun region of Inner Mongolia, Chi- Eocene at Tsagan Khutel, central Mongolia
na (fig. 1). The majority of these remains (Russell and Zhai, 1987); Eogrus turanicus
have been identified as part of a radiation of (Bendukidze, 1971) from middle-upper Eo-
crane-like, cursorial birds and placed in ei- cene near the Kalmakpai River, Kazakhstan;
ther the Eogruidae or the Ergilornithidae and Sonogrus gregalis (Kurochkin, 1981)
families (Wetmore, 1934; Kozlova, 1960; from the upper Eocene—lower Oligocene ex-
Kurochkin, 1976, 1981, 1982). Nearly all of posed at Khor Dzan (Sevkhul Member, Er-
these remains are distal pelvic limb elements: gilin Dzo Formation).
tibiotarsi and tarsometatarsi (Wetmore, 1934; Eogrus was placed in its own subfamily
Kozlova, 1960; Kurochkin, 1976, 1981, Eogruinae within the traditional suborder of
1982) although a coracoid, a proximal hu- Gruiformes, Grues, and the family Gruidae by
merus, as well as manual phalanges I:1 and Brodkorb (1967). Ergilornis, named by Ko-
2005 CLARKE ET AL.: EOCENE AVIAN FROM MONGOLIA 5
Zlova in 1960, was placed within a separate to Gruidae but with lateral trochlea of meta-
family within Grues, Ergilornithidae, which tarsus reduced and simplified in form, the leg
also includes the completely didactylous Mio- and foot being modified for running, legs
cene Amphipelargus (= Urmiornis, Harrison, long and slender ...’’. Modification for run-
1981, though see Karhu, 1997). In sum, five ning was inferred to be manifest in the con-
species of Eogruidae and seven of Ergilorni- formation of the distal tarsometatarsus in-
thidae (sensu Brodkorb, 1967) have been cluding, “‘robustness”’ of the metatarsal III
identified (reviewed in Kurochkin, 1981 and trochlea and reduction of the metatarsal I
Karhu, 1997). Stratigraphy seems to have and IV trochleae (Wetmore, 1934: 11). Weak
been taken into consideration in the identifi- development of the wing on the medial plan-
cation of subsequent eogruid species. For ex- tar surface of metatarsal H, with eight other
ample, it is doubtful that Eogrus wetmorei
morphologies of the tarsometatarsus and ti-
would have been diagnosed as a distinct spe-
biotarsus, was additionally identified to dif-
cies (Brodkorb, 1967) were it not for its mid- ferentiate the single species of Eogruidae he
dle Miocene age (Cracraft, 1973) especially
named (Wetmore, 1934: 3-4). Cracraft
since its diagnosis as smaller than that of
(1973), in his extensive review of fossil
Eogrus aeola (Brodkorb, 1967) does not hold,
Grues, revised the diagnosis of the Eogruidae
given the size range of specimens referred to
to include not only the reduction of the meta-
Eogrus aeola (e.g., AMNH 2946; fig. 8).
tarsal II and IV trochleae but also their lack
Wetmore (1934) considered eogruids
closely related to Gruidae (Cranes). Cracraft of plantar deflection.
(1969) mentioned a clade including Eogrui- A more marked reduction in the metatarsal
dae, Gruidae, Aramidae (Limpkin), and Pso- II trochlea relative to that observed in the
phiidae (Trumpeters) as supported, and later new fossil and in species of the family
figured (Cracraft, 1973: fig. 46) an Ergilor- Eogruidae is present in the traditional family
nithidae + Eogruidae clade as the sister tax- Ergilornithidae (Cracraft, 1973; Kurochkin,
on to a Gruidae, Aramidae + Psophiidae 1976, 1981, 1982; Olson, 1985). Indeed, Er-
clade (i.e., Cranes sister taxon of a Limpkin gilornithidae have been diagnosed by the re-
+ Trumpeters clade). Gruidae was placed as duction of metatarsal II trochlea to a “‘small
the sister taxon of Aramidae with alterna- stub”’ (e.g., Cracraft (1973: 73). Reduction of
tively Psophiidae (Livezey, 1998) or a Pso- the metatarsal II trochlea is considered here
phiidae + Opisthicomidae clade (Livezey to be diagnostic of a clade whose current
and Zusi, 2001) as its immediate outgroup. contents include the species recognized as
More recently a Gruidae + Aramidae clade parts of these two traditional families (e.g.,
with Psophiidae as its sister taxon was also
Brodkorb, 1967; Kurochkin, 1981; Karhu,
recovered from molecular data (e.g., Cracraft
1997). Eogruidae is used as the name for this
et al., 2004; Fain and Houde, 2004). A Pso-
clade as it was the first higher taxon name
phiidae + Gruidae clade was also recovered
proposed (Wetmore, 1934). Eogrus aeola
with bootstrap support (Aramidae was not in-
(holotype specimen, AMNH 2936; Wetmore,
cluded) in Mayr and Clarke (2003).
1934) is named as the internal specifier (sen-
INSTITUTIONAL ABBREVIATIONS: AMNH
American Museum of Natural History, New su Cantino and de Queiroz, 2000) for the
York; IGM Institute of Geology, Mongolian clade, as its first-named included species.
Academy of Sciences, Ulaan Baatar; PIN Pa- The contents of the traditional family
leontological Institute of the Russian Acad- Eogruidae may be paraphyletic with respect
emy of Sciences, Moscow. to Ergilornithidae. Indeed, Eogruidae was re-
peatedly suggested to be “‘ancestral’’ or to
SYSTEMATIC PALEONTOLOGY have given rise to Ergilornithidae (Cracraft,
AVES LINNAEUS, 1758 1973; Kurochkin, 1976, 1981, 1982). The
GRUES BONAPARTE, 1854 taxa included in the family Eogruidae were
GRUOIDEA VIGORS, 1825 distinguished from Ergilornithidae by reten-
EOGRUIDAE WETMORE, 1934 tion of the following plesiomorphic mor-
The original diagnosis of the family phology for Grues (and for Aves generally):
Eogruidae (Wetmore 1934: 3) was “related the presence of a comparatively less reduced
6 AMERICAN MUSEUM NOVITATES NO. 3494
metatarsal II trochlea (Cracraft, 1973; Ku- the Discussion); however, it is here consid-
rochkin, 1976, 1981, 1982). ered Eogruidae incertae sedis pending direct
*““Eogruidae”’ is recommended, but not de- comparison with the other named eogruid
fined, as an apomorphy-based name (de species (e.g., Sonogrus gregalis; Kurochkin,
Queiroz and Gauthier, 1992) for the clade, 1981; see Discussion) and the discovery of
including all taxa with a reduced, or lost, relevant new material. If further reduction of
metatarsal II trochlea homologous with the metatarsal II trochlea is found to diag-
Eogrus aeola. The taxon Ergilornithidae is nose an Ergilornithidae clade within the pro-
not revised or defined here. The name Ergi- posed Eogruidae clade, as appears supported,
lornithidae is used here to refer to contents then IGM 100/1447 is outside of this Ergi-
specified by the last revisers of the taxon lornithidae clade.
(Kurochkin, 1981; Karhu, 1997). These con-
tents are considered part of the clade Eogrui-
DESCRIPTION OF THE
dae as the name is used in the current paper.
NEW SPECIMEN
It is clear that taxonomic conventions main-
taining Ergilornithidae at the same rank as IGM _ 100/1447 is a nearly complete right
Eogruidae confound more than they clarify tarsometatarsus (fig. 2). It is from a species
understanding about the evolution of this close in size to extant species of Gruidae in-
group. cluding, for example, Balearica pavonina
Specimen IGM 100/1447 is identical to (Black-Crowned Crane; e.g., AMNH 10775).
Eogrus aeola for the morphologies repre- The tarsometatarsus of IGM 100/1447 is just
sented by 24 cladistic characters from the slightly shorter than that of this species. A
Livezey (1998) dataset and 7 characters from small portion of the lateroplantar surface of
the Mayr and Clarke (2003) dataset (e., the hypotarsus and the intercotylar area are
those preserved and able to be evaluated in missing (fig. 2A, E). The intercotylar process
the new fossil; appendix 1). It is referred to is well projected and dorsally bulbous with
Eogruidae on the basis of proposed autapo- a defined, curved dorsodistal margin (fig.
morphies of the distal tarsometatarsus ap- 2C). The dorsal openings of the proximal
proaching the morphologies referenced by vascular foramina are subequal in size, ad-
previous diagnoses (e.g., Wetmore, 1934; jacent, and set in a deep infracotylar fossa
Cracraft, 1973) and considered to diagnose (fig. 2C). Their plantar exits are also sube-
an Eogruidae clade relative to other Grues qual in size with the lateral placed just slight-
(sensu Livezey, 1998). All of these apomor- ly distal to the medial (compare fig. 2B, D).
phies are of the metatarsal I] trochlea and Several additional smaller foramina are de-
could describe the reduction in this trochlea veloped on the dorsal tarsometatarsal mid-
noted previously (Wetmore, 1934; Cracraft, line, proximal and distal to the paired foram-
1973). The description of these characters ina and to the well-projected tubercles of the
follows. The metatarsal II trochlea is propor- m. tibialis cranialis, respectively (fig. 2C).
tionally narrower in Eogruidae. It lacks a me- The extensor retinaculum tubercles on the
dioplantar wing, a more extreme condition proximodorsal surface of metatarsal II are
than seen in other Grues, and than those also well developed (fig. 2C).
compassed by Livezey (1998: 2121, charac- The parahypotarsal fossae are shallow
ter 351:0). Additionally, the metatarsal II with the medial slightly deeper than the lat-
trochlea is slightly less plantarly projected eral. The medial fossa extends well distal to
than that of IV (figs. 2E 6C). Weak plantar the hypotarsus. There is only one hypotarsal
projection (the metatarsal II trochlea equal to canal developed in the hypotarsus, which is
that of IV in extent) is addressed by Livezey medially located and is inferred to corre-
(1998: 2121, character 352: 0), however, the spond to Canal I of Strauch (1978; fig. 2A,
metatarsal II trochlea being less projected E). There is a smoothly angling lateral mar-
plantarly than IV is not compassed by the gin to the distal opening of this canal that
character states identified. continues into the distally extensive lateral
It is possible that IGM 100/1447 repre- hypotarsal ridge. This lateral hypotarsal crest
sents a new species (see further comments in extends farthest distally (fig. 2A), while the
2005 CLARKE ET AL.: EOCENE AVIAN FROM MONGOLIA 7
medial crest is projected farthest plantarly
(fig. 2E). The two laterally developed, ex-
tremely superficial hypotarsal sulci in Eogrus
daeola (Wetmore, 1934) may also have been
present, but the bone surface in the new fos-
sil is inadequately preserved to discern this
with confidence.
The shaft of the tarsometatarsus is robust,
with its proximal and distal ends notably
broad for its length, especially when com-
pared with the Eogrus aeola holotype and
referred specimens (compare figs. 2, 3). The
lateral plantar crest is very well projected,
although its plantar projection appears slight-
ly exaggerated by breakage (fig. 2A). The
medial crest extends farther proximally than
this lateral crest to reach the medial edge of
the hypotarsus. It bounds one side of a com-
paratively pronounced flexor sulcus distally
(fig. 2A).
The trochlea of metatarsal I is conspicu-
ously narrower than that of metatarsal IV
(fig. 2F) and is approximately one half the
width of that of metatarsal III. The metatarsal
Ill trochlea is proportionally broader than
that of Eogrus aeola (compare figs. 2, 3).
Neither the metatarsal II nor the metatarsal
IV trochlea is significantly plantarly deflect-
ed, and both lack pronounced wings on their
medial and lateral plantar edges, respectively
(fig. 2F). Metatarsal IV exceeds II slightly in
distal extent and plantar deflection. Fossa
metatarsi I is not strongly demarcated but
rather developed as a broad, shallow concav-
ity (fig. 2A).
PHYLOGENETIC ANALYSES
Analyses of two datasets (Mayr and
Clarke, 2003 for Aves; Livezey, 1998 for
<
middle Eocene Irdin Manha Formation: (A)
AMNH 2936, the Eogrus aeola holotype speci-
men, (B) AMNH 2937, referred to Eogrus aeola
and figured in Wetmore (1934). Wetmore (1934)
figured the distal tarsometatarsus of an Eogrus
aeola referred specimen (AMNH 2937; fig. 3B,
5B, 6C, this paper) and not the holotype specimen
(Wetmore, 1934: fig. 2). In the holotype specimen
(AMNH 2936) the metatarsal IV trochlea was
broken and improperly reattached (figs. 3A, 5A,
Big 23. Two right tarsometatarsi (in dorsal 6A). Anatomical abbreviations: pvf proximal vas-
view) collected in 1928 from a quarry at the cular foramen, rap reattachment point of broken
Chimney Butte locality, Shara Murun region, distal metatarsal II, tet tibialis cranialis tubercles.
8 AMERICAN MUSEUM NOVITATES NO. 3494
Fig. 4. Proximal ends of the right tarsometatarsi comprising (A) the holotype, AMNH 2936, and
(B) a referred specimen, AMNH 2937, of Eogrus aeola in proximal view. Anatomical abbreviations:
he hypotarsal canal, ica intercotylar area, tub muscular tubercle.
Grues) investigated the systematic position addition (branch swapping: tree-bisection-re-
of the new fossil and Eogruidae. The more connection) were performed holding only
completely known Eogrus aeola was used as one tree at each step. No more than 10 trees
an exemplar for Eogruidae in these analyses. one step longer than the shortest were re-
The Eogrus aeola terminal was scored from tained in each replicate. Branches were col-
AMNH 2936, the Eogrus aeola holotype lapsed to create polytomies if the minimum
specimen, as well as from AMNH 2937 and branch length was equal to zero. With the
AMNH 2946, referred to Eogrus aeola. same settings as in the primary analysis,
Character entries for this terminal in the two 1000 bootstrap replicates were also _per-
datasets were identical to that for the new formed.
fossil, IGM 100/1447 (and to the Eogrus Three most parsimonious topologies re-
wetmorei holotype, AMNH 2949), for all sulted (Length: 819, CI: 0.33, RI: 0.48, RC:
scored characters in common (appendix 1). 0.16). The strict consensus cladogram of
The metatarsal II trochlea characters present these trees recovered a Psophiidae + Eogrus
in IGM 1000/1447, and Eogruidae more daeola + Gruidae clade (fig. 9). Six unambig-
broadly (see Systematic Paleontology), were uously optimized synapomorphies supported
unique among the taxa sampled. As such, this clade in all three most parsimonious
they would not have been uninformative for, trees (1.e., 36:1 otic process of quadrate with
and were not included in, the phylogenetic a cluster of small pneumatic openings, 56:1
analyses. notarium present, 71:2 sternum with 7-8
Seven characters from Mayr and Clarke sternal rib articular surfaces, 72:1 dorsal sur-
(2003) could be evaluated for the new fossil face of sternum with numerous pneumatic
(see appendix 1) while these and an addi- foramina, 73:1, caudal margin of sternum
tional two tibiotarsal characters could be with two notches/fenestrae, 102:1 distal rim
scored for Eogrus aeola. Analysis of the of medal condyle of tibiotarsus notched) al-
complete Mayr and Clarke (2003) dataset though this clade was not recovered in great-
with the Eogrus aeola terminal was _ per- er than 50% of the bootstrap replicates. Char-
formed using PAUP*4.08b (Swofford, 2002) acter 102:1, the presence of a notch in the
and the same heuristic search parameters as medial condyle of the distal tibiotarsus, is the
in the primary analysis of the original pub- only one of these unambiguously optimized
lication: 1000 replicates of random stepwise synapomorphies preserved in Eogrus aeola.
2005 CLARKE ET AL.: EOCENE AVIAN FROM MONGOLIA 9
)
sens
Fig. 5. Distal ends of the right tarsometatarsi comprising (A) the holotype, AMNH 2936, and (B)
a referred specimen, AMNH 2937, of Eogrus aeola in plantar view. Anatomical abbreviations: mpc
medial plantar crest, rap reattachment point of broken distal metatarsal I.
The Livezey (1998) Grues dataset with the characters could be scored for Eogrus aeola.
addition of the Eogrus aeola terminal and the The suborder Grues dataset of Livezey
new fossil was then analyzed using (1998) was modified to exclude detailed re-
PAUP*4.08b (Swofford, 2002). Twenty-four consideration of Ralloidea interrelationships.
characters from Livezey (1998) could be Six taxa placed as parts of the basal three
evaluated for the new fossil (see appendix 1) divergences within Ralloidea were included
while these and nine additional tibiotarsal (of the 204 Ralloidea sampled in Livezey,
Fig. 6. Tarsometatarsi of the (A) holotype specimen of Eogrus aeola, AMNH 2936 (right side), and
referred specimens (B) AMNH 2946 (left side), and (C) AMNH 2937 (right side) in distal view.
10 AMERICAN MUSEUM NOVITATES NO. 3494
Big ei. The (A) left manual phalanx II:1 in ventral view and (B) left distal tarsometatarsus in dorsal
view of AMNH 2946, a specimen (or possibly specimen “‘lot’’; see Wetmore, 1934: 9) referred to
Eogrus aeola and collected from Camp Margetts, Shara Murun region, Irdin Manha Formation in 1930.
1998) to represent this clade (1.e., Heliopais 1447 as part of Gruoidea (sensu Livezey,
personata, Podica senegalis, Heliornis fuli- 1998; this paper, fig. 10). One character
ca, Himantornis haematopus, Gymnocrex ro- placed IGM 100/1447 closer to an Aramidae
senbergii, and Gymnocrex plumbeiventris; + Gruidae clade than to Psophiidae (353:0,
Livezey, 1998: fig. 1). trochlea metatarsi II subequal to IV in distal
The 26 ingroup terminals and the one out- projection, distal end reaching approximately
group, “Ancestor 2” of Livezey (1998), middle of trochlea metatarsi IV; fig. 10), and
were first analyzed in a branch and bound the plesiomorphic states for two characters
search including IGM 100/1447. Branches place the new fossil outside Aramidae +
were collapsed to create polytomies if the Gruidae clade (351:0 trochlea metatarsi II
minimum branch length was equal to zero. ‘“‘eminentia plantaris”’ [Livezey, 1998], or la-
Of the 570 characters in the Grues dataset teroplantar wing, moderately developed rath-
(Livezey, 1998), 205 were parsimony infor- er than conspicuously enlarged [fig. 2A, F];
mative (21 of which were specified as or- and 352:0 plantar extent of trochlea metatarsi
dered per Livezey, 1998) for the reduced II less than that of trochlea metatarsi IV [fig.
number of included taxa. Eight most parsi- 2F]). Monophyly of Gruidae is supported by
monious trees (Length: 340, CI: 0.74, RI: 12 optimized synapomorphies (59:1, 103:4,
0.91, RC: 0.67) resulted. A strict consensus 15521, 22421, 23471, 25870, 32521, 3411,
cladogram of these trees recovered IGM 100/ 371:2, 476:1, 487:2, 533:2). 1000 bootstrap