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Verlag Dr. Friedrich Pfeil • München
Gloria Arratia, Hans-Peter Schultze
and Mark V. H. Wilson
(editors)
Mesozoic Fishes 5
Global Diversity and Evolution
Proceedings of the international meeting
Saltillo, 2010
291
Mesozoic Fishes 5 – Global Diversity and Evolution, G. Arratia, H.-P. Schultze & M. V. H. Wilson (eds.): pp. 291-303, 6 figs.
© 2013 by Verlag Dr. Friedrich Pfeil, München, Germany – ISBN 978-3-89937-159-8
Teleost centrum and jaw elements
from the Upper Cretaceous Nemegt Formation
(Campanian-Maastrichtian)
of Mongolia
and a re-identifi cation of the fi sh centrum
found with the theropod Raptorex kreigsteini
Michael G. NEWBREY, Donald B. BRINKMAN, Dale A. WINKLER,
Elizabeth A. FREEDMAN, Andrew G. NEUMAN, Denver W. FOWLER
and Holly N. WOODWARD
Abstract
Isolated centra and a premaxilla of a teleost from the Upper Cretaceous Nemegt Formation (Late Campanian-
Early Maastrichtian) of Mongolia are described and aligned with the hiodontids and the Late Cretaceous
teleost Coriops from North America. The atlas of the Nemegt taxon has an anterior articular surface with the
dorsal half being subdivided into two flat articulator surfaces as in those of the hiodontids. In more posterior
abdominal centra, the centrum is strongly constricted at the notochord foramen, the rib loosely articulates in a
facet on the lateral wall of the centrum posterior to the parapophysis as in hiodontids, and parapophyses are
fused to the centrum. Neural arch articular facets are small and round. Distinct mid-dorsal foramina are absent
or small and poorly developed. A single stout premaxilla is relatively straight and has a low rounded dorsal
margin on the posterior end. There are two rows of strong conical teeth and the tooth bases of the lateral row
protrude laterally. The Nemegt centra are then used to re-identify a teleost centrum associated with the Asian
theropod, Raptorex kreigsteini. Initially the fish centrum found with R. kreigsteini was assigned to Lycoptera. The
stratigraphic range of Lycopteridae, ~120-135 Ma, was used to infer an age of deposition for the basal taxon
Raptorex. Subsequently this centrum was re-identified as a clupeomorph centrum. However, centra of Lycoptera
are mainly comprised of the chordacentrum surrounded by a very thin autocentrum, thus giving the appearance
of being tubular with an unconstricted notochordal foramen; they are thin-walled, small (≤ 2 mm diameter), and
may have a broad bar (presence depends on the species and ontogenetic development) extending the length of
the centrum in lateral view. Parapophyses are not fused with the autocentrum and articulate with the centrum
at large facets as in those of lower teleosts. Pleural ribs in Lycoptera articulate with the parapophyses. The fish
centrum found with R. kreigsteini is of a higher teleost with a well-developed autocentrum strongly constricting
the notochord, thereby giving the centrum an amphicoelous shape. This centrum has several aspects in common
with the Nemegt Formation teleost centra: poorly developed mid-dorsal foramen; shape and position of the facets,
where the arch articulates, being circular and located near the anterior end of the centrum; presence of short,
fused parapophyses at the ventro-lateral corner of the centrum; lateral surface of the centrum bearing a series of
foramina of small to moderate size that are generally organized into rows. Thus we reject the hypotheses that
the fish centrum found with R. kreigsteini has affinities with the Lycopteridae or the Clupeomorpha and reassign
the centrum to the hiodontids. The morphological characteristics of the fish centrum found with R. kreigsteini
suggest a Late Cretaceous hiodontid-like taxon and thus its co-occurrence with Raptorex suggests that dinosaur
is an Upper Cretaceous theropod.
292
Introduction
Little is known of fishes from the fluvial beds of the Upper Cretaceous of Mongolia. Fish remains are present
in some localities, often in great abundance, but as is typically the case for fluvial beds, are represented
exclusively by isolated elements (NEUMAN & BRINKMAN 2005). While such material presents challenges,
study of such material from the Upper Cretaceous of Alberta, Canada, shows that useful information
regarding biology, distribution, diversity, and first occurrences of major groups can be obtained (BRINK-
MAN & NEUMAN 2002; NEWBREY et al. 2007, 2008, 2010). In this study, isolated centra and jaws from
the Nemegt Formation of Mongolia are described and compared with similar elements from the Upper
Cretaceous of North America. Specifically, we compared centra of a taxon from the Nemegt Formation
to those of hiodontids and Coriops to test the idea of close taxonomic affinity. Our second goal was to
examine an isolated centrum of uncertain locality referred to Lycoptera by SERENO et al. (2009) and the
Ellimmichthyiformes by FOWLER et al. (2011), with the purpose of discussing its taxonomic affinity.
Materials and methods
Institutional abbreviations
FOBU, Fossil Butte National Monument, Kemmerer, Wyoming, USA; LACM, Natural History Museum of Los
Angeles County, Los Angeles, California, USA; MPC-KID, Geological Institute, Academy of Sciences, Ulaan
Baatar, Mongolia; TMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada; UALVP, Labo-
ratory for Vertebrate Paleontology, University of Alberta, Edmonton, Alberta, Canada; USNM, Smithsonian
Institution National Museum of Natural History, Washington DC, USA.
Fossil material examined
Ellimmichthyiformes: Diplomystus dentatus COPE, 1877, n = 34, Green River Formation, Eocene: LACM 133801,
54095; TMP 1986.224.0081, 1986.224.0084 (n = 2), 1986.224.0085, 1986.224.0086, 1986.224.0089, 1986.224.0091 (n = 2),
1986.224.0092, 1986.224.0135, 1989.124.0002; UALVP 226, 228, 2049, 17731, 20318, 20331, 21021, 21025, 21027,
21041, 21072, 21155, 22860, 52161, 21163, 52157, 52173, 52183, 52205, 52229; USNM 1707. Horseshoeichthys sp.
NEWBREY et al. 2010, n = 10, Milk River (Santonian), Oldman and Dinosaur Park formations (Campanian): TMP
1986.010.0064, 1986.021.0063, 1986.038.0045, 1993.093.0097, 1993.093.0103, 1995.180.0031, 2001.045.0093; UALVP
48871, 48872, 48873.
Osteoglossomorpha, Lycopteridae: Lycoptera davidi (SAUVAGE, 1880), n = 55, Early Cretaceous: UALVP 44031
(n = 10); USNM 16616 (n = 20), 18199 (n = 8), 18268 (n = 17).
Hiodontiformes: Coriops ESTES, 1969, n = 74: TMP 1993.117.0007 (n = 27), 1995.006.0054 (n = 47) (BRINKMAN &
NEUMAN 2002).
Hiodontidae: Eohiodon woodruffi WILSON, 1978, n = 2: FOBU 13276, UALVP 31948; hiodontid (n = 14): TMP
1986.037.0085, 1986.060.0032a, 1986.179.0006, 1986.198.0042, 1986.242.0068b, 1987.032.41, 1987.158.0029b,c,
1990.113.0057a, 1993.093.0094, 1995.147.0002, 1995.168.0047, 1995.182.0034 (BRINKMAN & NEUMAN 2002,
specimens from NEWBREY et al. 2007).
Methods
Centra were described using the terminology of SCHULTZE & ARRATIA (1989), ARRATIA et al. (2001), and
HILTON (2002). Comparisons of size among centra were made in two ways: absolute diameter of abdominal
vertebral centra and diameter of those centra plotted against standard length (SL, distance from anterior tip of
head to posterior tip of the second ural centrum). Means, standard errors (SE), and a 99 % confidence interval (CI)
were calculated for each taxon. An Analysis of Variance (ANOVA) with Bonferroni post-hoc tests was used to
determine if there were significant differences between centrum diameters of Lycoptera and other taxa examined.
Statistical tests were performed with SYSTAT (2004) and alpha was set at 0.05 unless otherwise specified.
The Raptorex-associated teleost centrum (SERENO et al. 2009: fig. S8) was compared to the 99 % prediction
interval (PI) of the relationship between SL and centrum diameter for Lycoptera. A single centrum was randomly
selected from each fish for inclusion in the dataset. Height of vertebral centra and SL of Lycoptera taxa were
measured using a digital caliper (mm) for each taxon. Plotting centrum diameter by SL provides a relative growth
trajectory to check for an asymptote in size, reducing the possibility of making a Type I error. A quadratic least
squares regression was used to describe the relationship between SL and centrum diameter of Lycoptera. Diameters
of centra were also measured directly from specimens in the UALVP and USNM collections and from published
293
images of L. fuxinensis (ZHANG 2002: fig. 1A,C) and L. davidi (ZHANG 2002: fig. 2A). In all, the diameters of 46
centra were measured from L. davidi and three centra (n = 2 diameters associated with SL data) of L. fuxinensis
from ZHANG (2002).
Systematic paleontology
Class Actinopterygii COPE, 1887
Teleostei MÜLLER, 1845
Order Hiodontiformes TAVERNE, 1979
Family Hiodontidae CUVIER & VALENCIENNES, 1846
Fig. 1A-F
Material: MPC-KID 2006.002-01, -02, -03, -04, -05, -06.
Localities and strata: Ulan Khushu locality, Nemegt Formation, Gobi Desert, Mongolia.
Age: Late Campanian-Early Maastrichtian.
Description of Nemegt fossils
Centra. Morphological variation along the vertebral column was documented by a series of 130 centra
from a single locality. Position in the vertebral column was estimated from comparison with extant teleosts,
particularly clupeomorphs and osteoglossomorphs. Five centra illustrated in Figure 1 document the major
features of the abdominal column.
The autocentra are large in diameter and originated from dysospondylous type vertebrae. Length
is typically shorter than or equal to width. The notochord is strongly constricted giving the centrum an
amphicoelous shape. Articular facets, where the neural arch articulates, are small and round. Distinct
mid-dorsal foramina are absent or poorly developed. Parapophyses are fused to the centrum and they
occur laterally as nearly transverse processes on anterior abdominal centra, but their orientation shifts to a
more ventrolateral position in posterior abdominal centra. Anterior parapophyses are robust and distally
curve ventrolaterally. Ventrolateral parapophyses are directed ventrolaterally.
Atlas centra (Fig. 1A) are short and small and are distinguished by the presence of an anterior articular
surface. The dorsal half of this is like the atlas of hiodontids in being subdivided into two flat articular
surfaces. However, in contrast with the hiodontid atlas, a corresponding pair of articular surfaces is not
present ventrally. Transverse processes are absent and the neural arch articular facets are located towards
the posterior end of the centrum.
Anterior abdominal centra (Fig. 1B,C) are shorter than long and have long, laterally directed parapo-
physes. The rib loosely articulates in a facet on the lateral wall of the centrum. The facet is immediately
posterior to the parapophysis and the parapophysis probably provides additional support along the ante-
rolateral edge of the pleural rib. The neural arch articular facets are located in the middle of the centrum
and are separated by a solid bar of bone. The ventral surface of the centrum has one to three elongate
fossae.
Mid-abdominal centra (Fig. 1D) have reduced parapophyses that slope ventrolaterally. As in more
anterior abdominal centra, the rib loosely articulates in a facet on the lateral wall of the centrum just pos-
terior to the parapophysis. The parapophysis in mid-abdominal centra probably also provides additional
support to the pleural rib. Neural arch articular facets are located in the middle of the centrum and are
separated by a single bar of bone, although slightly larger foramina anticipate the presence of mid-dorsal
foramina present in more posterior centra. The ventral surface of the centrum has a single elongate mid-
ventral foramen. The centrum is relatively longer than the anterior abdominal centra.
Transitional abdominal centra (Fig. 1E) have greatly reduced parapophyses that are distally incomplete
and located at the ventrolateral corner of the centrum. The neural arch articular facets are located towards
the anterior end of the centrum. Mid-dorsal fossae are present anterior and posterior to the neural arch
articular facets. The lateral surface of the centrum between the parapophysis and neural arch articular
facets is covered with multiple foramina of small to moderate size. The ventral surface of the centrum has
a single elongate mid-ventral fossa. As with the mid-abdominal centra, the posterior abdominal centra are
sub-equal in length and width.
294
Premaxilla. Jaw elements are represented by a partial right premaxilla (Fig. 1F). The premaxilla is stout,
with a low rounded dorsal margin on the posterior end (Fig. 1F: labial view). The anterodorsal margin is
slightly raised. The lingual face is slightly concave (Fig. 1F: lingual view). The premaxilla is relatively straight
and bears two rows of strong conical teeth (Fig. 1F: occlusal view). The anterior teeth are more robust than
the posterior teeth. Tooth bases of teeth in the labial row protrude laterally (Fig. 1F: labial view).
A
B
C
D
E
F
Fig. 1.
Centra and a premaxilla from the Nemegt Formation, Mongolia. Centra (A-E) are depicted from left to right in
five views: anterior, left lateral, posterior, dorsal, and ventral. A, atlas (MPC-KID 2006.002-01). B-C, anterior
dorsal, precaudal centra (MPC-KID 2006.002-02, -03); D, mid-dorsal precaudal centrum (MPC-KID 2006.002-04).
E, posterior dorsal precaudal centrum (MPC-KID 2006.002-05). F, left premaxilla (MPC-KID 2006.002-06) in three
views: labial, lingual, and occlusal. Scale bars: A-E = 2 mm; F = 1 mm.
295
Comparisons
All the centra examined were consistent with a single type of teleost. This is interpreted as a hiodontid
primarily because of the features of the atlas centrum. As in hiodontids, flat bipartite articular surfaces
are present dorsally and the neural arch articular facets are small, circular, and located on the posterior
half of the centrum (BRINKMAN & NEUMAN 2002). Similarities with the atlas of the hiodontids from the
Late Cretaceous of North America (Fig. 2A) when seen in dorsal view are particularly striking. As well as
being similar in the shape of the anterior articular surfaces and the size, shape, and position of the neural
arch articular facets, the centra of these two taxa are also similar in the position of a small mid-dorsal fossa
anterior to the neural arch articular facets.
The atlas centra of the Nemegt taxon lack a flat bipartite articular surface on the ventral half of the atlas
centrum that is present in hiodontids from North America, including the Late Cretaceous taxon from the
A
B
C
D
E
F
Fig. 2.
Centra of Hiodontidae from the Dinosaur Park Formation, Alberta, Canada. Centra are depicted from left to
right in five views: anterior, left lateral, posterior, dorsal, and ventral. A, atlas (TMP 2005.012.0569). B, anterior
precaudal centrum (TMP 1995.181.0034d). C-D, mid-precaudal centra TMP 1995.181.0034b, 2000.006.0003c).
E-F, posterior precaudal centra (TMP 1995.181.0034a, 2000.006.0003a). Scale bars: A-F = 1 mm.
296
Dinosaur Park Formation (Fig. 2A). Instead of such a surface, the ventral surface of the centrum forms a
sharp edge. As well, rather than a flat ventral surface formed by a network of bone, the atlas centrum of
the Nemegt taxon has a mid-ventral fossa separating a pair of robust rounded ridges extending antero-
posteriorly.
The more posterior abdominal centrum is similar to those of hiodontids (HILTON 2002) in having long
parapophyses with pleural ribs loosely articulated in deep facets directly on the lateral wall of the centrum
posterior to the parapophyses. As in extant Hiodon, the parapophyses provide additional support for the
pleural ribs. They differ in that the neural arch articular facets are relatively small and round throughout
the length of the vertebral column, rather than being elongate oval neural arch articular facets that nearly
extend the full length of the centrum as in Late Cretaceous hiodontids from North America (Fig. 2B-D)
(BRINKMAN & NEUMAN 2002).
The Nemegt premaxilla is similar to premaxillae attributed to Coriops in having multiple rows of strong,
conical teeth (Fig. 1F). In the Nemegt taxon, two rows of teeth are present, as is typically the case in the
premaxilla of Coriops (Fig. 3F-G). HILTON (2002) reports that most specimens of extant Hiodon have one
row of teeth but some may have two rows anteriorly. Both taxa have more robust teeth anteriorly and
protruding tooth bases laterally. They differ in that the teeth of the labial tooth row of Coriops are located
on the lateral surface of the premaxilla and those teeth are curved such that the crowns point ventrally.
In the Nemegt taxon, both rows of teeth are located on the ventral surface of the premaxilla and the teeth
of both rows are relatively straight in a ventral direction (Fig. 1F). Furthermore, the premaxilla of Coriops
has a strong medial bend, while the Nemegt taxon is relatively straight. The premaxilla of the Nemegt
teleost lacks an anterior ascending process as is also the case for Paleogene and extant hiodontids (LI
& WILSON 1994, LI et al. 1997, HILTON 2002, HILTON 2003, HILTON & GRANDE 2008). In contrast,
Coriops, Lycoptera, and other osteoglossomorphs have an ascending process on the premaxilla (MA 1987,
HILTON 2003: fig. 17, HILTON & GRANDE 2008).
Taxonomic affinities of Nemegt Formation centra
The centra of the Nemegt taxon are similar to centra attributed to Coriops in the presence of long, laterally
directed parapophyses with rib articular facets located on the lateral wall of the centrum posterior to the
parapophyses (NEUMAN & BRINKMAN 2005: fig. 9.8D). Additional similarities with Coriops are suggested
by similarities in the premaxilla of the Nemegt taxon and that of Coriops (Fig. 3F, G). Unfortunately, tooth-
bearing elements of Late Cretaceous hiodontids from North America have not been identified, although
the presence of multiple rows of large conical teeth is also consistent with the condition in extant members
of Hiodon (HILTON 2002).
The centra of the Nemegt taxon are similar to hiodontid centra in the development of the anterior
articular surface of the atlas and of the articular facets on the dorsal surface. The presence of similarities
with both Coriops and hiodontids is consistent with the suggestion that Coriops is closely related to the
Hiodontidae (BRINKMAN et al. in press). Thus the similarities of the atlas of the Nemegt taxon with
hiodontids suggests that it is more closely related to that family than is Coriops, but the absence of fully
developed quadratic articular surface on the atlas suggests that it is basal to other members of that fam-
ily.
Since hiodontids are relatively basal osteoglossomorphs (WILSON & MURRAY 2008), which are in
turn sister to the Clupeocephala (sensu ARRATIA 2010a), comparison with that group is warranted. Two
ellimmichthyiform clupeomorphs were examined from the Cretaceous Sorbinichthyidae, Horseshoeich-
thys armaserratus, and the Eocene Paraclupeidae, Diplomystus dentatus. Descriptions and figured centra
from H. armaserratus and D. dentatus are provided by NEWBREY et al. (2010). These centra are strongly
amphicoelous and robust (Fig. 4A-E). Two anteriorly placed neural arch articular facets generally occur
on the anterior half of the centrum (FOBU 11661, TMP 1993.091.0021; BRINKMAN & NEUMAN 2002:
fig. 2). The neural arch articular facets may or may not be separated by the large mid-dorsal fossa that
occurs primarily on the posterior half of the centrum (TMP 1993.091.0021, 1986.021.0063; BRINKMAN &
NEUMAN 2002: fig. 2; Fig. 4D). In H. armaserratus, as in the Nemegt taxon, the neural arch articular facets
are circular and are small relative to the length of the centrum (Fig. 4D). This is also the case in the more
posterior abdominal centra of Diplomystus dentatus. The mid-dorsal fossa may or may not be subdivided
into two lateral halves. Separate single or double fossae follow each of the neural arch articular facets
in dorsal view (TMP 1993.091.0021; BRINKMAN & NEUMAN 2002: fig. 2). Laterally, the parapophyseal
articular facets occur on the lower half of the centrum (Fig. 4B). Dorsal to the parapophyseal articular facet
297
A
B
C
D
E
FG
HI
Fig. 3.
Centra, premaxillae, and dentaries of Coriops from the Dinosaur Park Formation, Alberta, Canada. Centra (A-E)
are depicted from left to right in five views: anterior, left lateral, posterior, dorsal, and ventral. Right premaxillae
(F-G) are depicted left to right and top to bottom in three views lateral, medial, and occlusial. Right dentaries
(H-I) are depicted left to right and top to bottom in three views: lateral, medial, and occlusial. A, anterior
precaudal centrum (TMP 1986.044.0043a). B-D, mid-precaudal centra (TMP 1995.177.0067b, 1995.177.0067a,
1987.004.0018a). E, posterior precaudal centrum (TMP 1990.115.0046a). F, premaxilla (TMP 2000.006.0028a).
G, premaxilla (TMP 1990.033.0064a). H, dentary (TMP 1986.043.0033); dentary (TMP 1990.119.0035a). Scale bars:
A, B, E-I = 2 mm; C, D = 1 mm.
298
is a large, subdivided fossa that extends the full length of the centrum (TMP 1986.038.0045) or a series
of small foramina arranged in an irregular manner (TMP 1986.021.0063). Thus, overall, the centra of the
Nemegt hiodontid, as with hiodontids from the Upper Cretaceous of North America, are distinct from
those of ellimmichthyiforms.
The fish centrum found with Raptorex kreigsteini
With this understanding of the centrum morphology of the Nemegt teleost, the affinities of a centrum found
in association with a dinosaur described by SERENO et al. (2009) as Raptorex kreigsteini can be re-evaluated.
This centrum was recovered with that theropod, but the age and stratigraphic description of this material
is imprecisely known (SERENO et al. 2009, FOWLER et al. 2011). The possibility that it is from the Lower
Cretaceous lake beds of Liaoning was rejected because of the absence of laminated, fine-grained sediment
and conchostracans (SERENO et al. 2009). However, the presence of an unidentified clam and fish centrum
identified as “cf. Lycoptera” was used to suggest that Raptorex was from the Lujiatun Beds of the Yixian
Formation. Thus the age of Raptorex is based primarily on the identity of the fish centrum (SERENO et al.
2009: supp. info. figure 8, FOWLER et al. 2011). SERENO et al. (2009) inferred that the Raptorex locality
was within the age range ~130 Ma (p. 419) to 125 Ma as stated in their figure 4A. Fossils of Lycoptera are
known from Lower Cretaceous deposits (CHANG & MAIO 2004, ARRATIA 2010b) and range in age from
122-135 Ma (LI et al. 1994) or 120-133 Ma (CHEN & CHEN 1997, WANG et al. 1999: 8). Thus the identity
of the centrum has profound implications for the stratigraphic age of R. kreigsteini. However, no description
was given by SERENO et al. (2009) for the fish centrum found with R. kreigsteini, and there are no thorough
descriptions of centra of Lycoptera in the published literature, so this identification has been questioned.
FOWLER et al. (2011) rejected the hypothesis that the teleost centrum found with Raptorex was that of a
lycopterid and suggested rather that it was related to an ellimmichthyiform; however, the analysis was
preliminary pending a more thorough review such as that in this work (FOWLER et al. 2011). The analysis
in FOWLER et al. (2011) bases its morphologic comparison mostly on the reported “large opening for the
notochord” of Lycoptera (ZHANG 2002: 265), but lacks a detailed, specimen-based description to address
the hypothesis that the fish centrum found with Raptorex is not of Lycoptera. To test the biostratigraphic
conclusions of SERENO et al. (2009) and FOWLER et al. (2011), the identity of the Raptorex teleost centrum
is re-evaluated by comparison to those of Lycoptera, the Nemegt teleost, and teleosts from North America
that are thought to be broadly related to the Nemegt teleost, particularly hiodontids, Coriops, as well as
the ellimmichthyiform Horseshoeichthys.
Description of the fish centrum found with Raptorex kreigsteini
The fish centrum found with Raptorex kreigsteini was illustrated with the dorsal, anterior, and right lateral
surfaces visible in SERENO et al. (2009: fig. S8); the SERENO et al. image of the fish centrum was repub-
lished in FOWLER et al. (2011). The centrum is re-figured as a line drawing here for ease of comparison
(Fig. 5A). This centrum originates from a dysopondylous vertebra and is rectangular in lateral view.
The centrum displays two small, round neural arch articular facets in the anterior half (Fig. 5A). The
centrum is strongly amphicoelous and the autocentrum is thick, thereby constricting the notochord. In
the posterior half of the centrum, a single, mid-dorsal fossa narrows anteriorly and does not separate the
neural arch articular facets. Two small fossae (i. e., extending anterior to posterior) occur behind the right
neural arch articular facet (FOWLER et al. 2011). In lateral view and on the dorsal half of the centrum,
Fig. 4.
Centrum of Cretaceous ellimmichthyiform, Horseshoeichthys sp. from the Oldman Formation (Campanian) (TMP
1995.180.0039). A, anterior. B, lateral. C, posterior. D, dorsal. E, ventral views. Scale bar = 1 mm.
EAB CD
299
there are several small foramina separated by fine ridges of bone (Fig. 5A). The parapophyses are fused
to the ventrolateral corners of the centrum. The diameter of the centrum is 4 mm (SERENO et al. 2009,
FOWLER et al. 2011).
Description of centra of Lycoptera
The morphology of centra of Lycoptera sp. is distinct among fishes examined in this study (Fig. 5B-F).
The centra originate from dysospondylous vertebrae and are thin-walled, being mainly comprised of
the chordacentrum in small individuals and surrounded by a thin autocentrum in larger individuals.
The centra are perforate being relatively unconstricted at the notochord foramen (UALVP 44031, USNM
16616). Strictly speaking, the notochordal foramen or the inside diameter of the chordacentra is no larger
in diameter than, for example, those of the hiodontids or ellimmichthyiforms (M.G.N. pers. obs.); it is the
walls of the autocentrum that are thinner than in other more advanced teleosts with well-developed auto-
centra. FOWLER et al. (2011) also correctly pointed out that centra of Lycoptera are tubular in appearance
and cited ZHANG (2002) for noting the tubular appearance of the centra, but this is imprecise. ZHANG
(2002) only stated that the opening for the notochord foramen is large, which is relative. Specifically, the
notochordal foramen represents 71 % of total centrum diameter (Fig. 5B-F). An unconstricted notochord
could also be present in young individuals, thereby giving the false perception that centra in the species
are tubular in appearance. FOWLER et al. (2011) stated that individuals of Lycoptera generally range in
size from 7 to 13 cm, and their centra are typically 1-2 mm long and cite MA (1987) and ZHANG (2002)
for the information. However, MA (1987) does not address these points and only figures posterior cau-
dal centra and ZHANG (2002) only states a range in size from 3.5 to 9 cm SL from a small sample (n = 8
complete specimens). GREENWOOD (1970) also noted the maximum recorded size of members of the
family was <12 cm in length but did not address the presence or absence of adults. However, our results
reveal the presence of a quantifiable “asymptote” in size of centra in longer individuals, thus confirming
the existence of adults in the sample.
The centra of Lycoptera davidi and L. fuxinensis remain small (thin) throughout life in the material
and taxa examined (n = 29) with no diameter exceeding 2 mm (Fig. 6A,B). An asymptote in size occurs at
1.6 mm centrum diameter and at 49 mm SL or greater for all Lycoptera taxa examined. In this study, the
99 % prediction interval calculated from the relationship between SL and centrum diameter of Lycoptera
does not exceed 2.6 mm centrum diameter and a clear “asymptote” is present, suggesting adults are
present in the sample and that autocentra stay small and thin, thereby maintaining a proportionally large
chordacentrum (Fig. 6A,B).
nf
Left
neural pit
Mid-dorsal
foramen
Laterodorsal
foramina
F
E
DC
B
A
Anterior
Laterally-crushed centra Anterior view of centrum
Fig. 5.
Centra of Cretaceous fishes. A, fish centrum found associated with Raptorex kreigsteini (SERENO et al. 2009:
fig. S8). B, Lycoptera davidi (UALVP 44031), rectangle indicates area magnified in ‘C’. C, precaudal and caudal
centra of L. davidi (UALVP 44031). D, anterior view of L. davidi centrum naturally broken in transverse section
through the anterior half. E, lateral view of a precaudal centrum of L. fuxinensis from ZHANG (2002: from
fig. 1C). F, interpretation of dorsal view of L. davidi (UALVP 44031, USNM 18199). Scale bars: A, C, E; B = 5 mm;
D, F = 0.5 mm. Abbreviations: nf, notochord foramen.
300
The autocentra of Lycoptera have neural arch articular facets that are very shallow and elongate but do
not extend the full length of the centrum (USNM 18199, UALVP 44031). No large, central foramen (mid-
dorsal) could be confirmed on the posterodorsal surface of examined centra of Lycoptera (Fig. 5F). Ante-
riorly, parapophyseal facets occur low on the centrum and ribs articulate on the parapophyses (ZHANG
2002: fig. 1C,D; USNM 18199; UALVP 44031). Parapophyseal facets extend most of length of the centrum
in the material examined.
Chordacentra are often crushed in a lateral plane (Fig. 5B-C) and up-turned to expose an anterior or
posterior view. This is especially common in specimens under 5 cm SL. The lateral faces of chordacentra
are smooth in small (<5 cm SL) specimens similar to those of leptolepids (see ARRATIA & HIKUROA
2010: fig. 7c). In larger specimens, the lateral faces of the autocentrum have a prominent ridge that extends
the full length of the centrum between the parapophyseal facet and a relatively large foramen (Fig. 5E).
The large foramen is anteriorly placed on the upper half of the lateral wall of the centrum and extends
50-70 % the length of the centrum (see ZHANG 2002: fig. 1C,D).
Fig. 6.
Centrum diameter (CD) and standard length (SL) of taxa of Lycoptera and hiodontiforms compared to the diameter
of the fish centrum found with Raptorex kreigsteini and figured in SERENO et al. (2009: fig. S8). A, the relation-
ship between SL and CD of two taxa of Lycoptera, solid black line represents a quadratic least squares regression
(R2 = 0.591, P < 0.001), solid gray lines represent 99 % prediction intervals (PI), broken line represents the diameter
of the SERENO et al. (2009) fish centrum. B, centrum diameter of the SERENO et al. (2009) fish centrum com-
pared to those of two taxa of Lycoptera, and three taxa of hiodontiforms: Nemegt Formation, Mongolia, a large
hiodontid (NEWBREY et al. 2007: growth profile 1 [GP1]) from the Dinosaur Park Formation, Alberta Canada,
and Coriops from the Dinosaur Park Formation, Alberta, Canada.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 10 20 30 40 50 60 70 80 90 100 110 120
SL (mm)
CD (mm)
Sereno et al. fish centrum
Lycoptera davidi
Lycoptera fuxinensis
99% P.I. for diameter
Lycoptera
Hiodontiformes
Nemegt Fm.
Dinosaur Park Fm.
Dinosaur Park Fm.
0
1
2
3
4
5
6
7
8
9
10
CD (mm)
Sereno et al. fish centrum
Mean
Lycoptera davidi
Lycoptera fuxinensis
Nemegt hiodontid
GP1 hiodontid
Coriops
A
B
301
Comparison of centra of Lycoptera to the fish centrum found with Raptorex kreigsteini
The fish centrum found with Raptorex kreigsteini differs from those of Lycoptera in being a well-developed
autocentrum of a higher teleost. The autocentrum is large in diameter with thick walls, having deep
amphicoelous ends (i. e., strongly constricting the notochord), fused parapophyses, and lacking a mid-
horizontal bar in lateral view. The walls of the autocentrum of Lycoptera are very thin and the centrum stays
small during ontogenetic development with the chordacentrum representing the majority of the centrum.
Parapophyses are not fused to the centrum and pleural ribs articulate on the parapophyses as with other
lower teleosts. The fish centrum found with R. kreigsteini is 33 % larger than the upper 99 % prediction
interval of the centrum diameters of taxa of Lycoptera examined in this study (n = 59, x = 0.96 ± 0.04 SE mm
diameter, Fig. 6A). This size difference adds further evidence that the fish centrum found with R. kreigsteini
is not from any known species of Lycoptera. Thus, based on morphological and phylogenetic differences,
we reject the hypothesis that the fish centrum found with R. kreigsteini is from a species of Lycoptera.
Comparison of centra of Horseshoeichthys to the fish centrum found with Raptorex kreigsteini
The fish centrum found with Raptorex kreigsteini is similar to mid-abdominal autocentra of the ellimm-
ichthyiform Horseshoeichthys in the presence of small, circular neural arch articular facets located near
the anterior end of the centrum, and based on this similarity, the fish centrum found with R. kreigsteini
was tentatively attributed by FOWLER et al (2011) to the Ellimmichthyiformes. However, this feature
is also present in the Nemegt teleost and not strongly indicative of a relationship. In other features, the
fish centrum found with R. kreigsteini differs substantially from those of examined ellimmichthyiforms.
These include the lack of prominent longitudinal ridges subdividing the lateral face and the presence of
parapophyses fused to the centrum of Cretaceous forms. Thus, despite the similarity in the shape of the
neural arch articular facets with that of some ellimmichthyiforms, we reject the hypothesis that the fish
centrum found with R. kreigsteini is of an ellimmichthyiform.
Comparison of centra of Nemegt teleost to the fish centrum found with Raptorex kreigsteini
The fish centrum found with Raptorex kreigsteini is similar to the posterior precaudal centra of the Nemegt
teleost (Fig. 1E) in proportions, shape and position of the neural arch articular facets, development of a
series of small foramina on the side of the centrum, and presence of a short parapophysis at the vent-
rolateral corner of the centrum. In both types, the centrum is subequal in length and width. The neural
arch articular facets are circular and located near the anterior end of the centrum. The lateral surface of
the centrum bears a series of foramina, small to moderate in size, that are generally organized into rows.
In both types, short, fused parapophyses are present on the ventrolateral corner of the centrum. Thus,
based on morphological features that can be observed, the fish centrum found with R. kreigsteini is likely
from the Nemegt taxon. To further test this identification, the fish centrum found with R. kreigsteini was
compared in size with 25 centra of the Nemegt teleost and two taxa from North America, Coriops and
the hiodontid from the Dinosaur Park Formation. The fish centrum found with R. kreigsteini plots out-
side the 99 % confidence interval for the Dinosaur Park Formation hiodontid (n = 14, x = 2.0 ± 0.17 SE mm
diameter), but falls within the range of sizes of centra from the Nemegt Formation (n = 25, x = 5.3 ± 0.20
SE mm diameter) and Coriops (n = 75, x = 3.9 ± 0.17 SE mm diameter) from the Dinosaur Park Formation
(Fig. 6B). Thus the size of the centrum is consistent with the hypothesis that the fish centrum found with
R. kreigsteini is from the Nemegt teleost. Since centra like those of the Nemegt teleost are not known from
outside the Nemegt Formation, this identification implies that R. kreigsteini is from the Upper Cretaceous
and probably from the Nemegt Formation.
The conclusion that the fish centrum found with R. kreigsteini is from the Nemegt teleost can be fur-
ther tested by examining features that are not currently visible in the SERENO et al. (2009) figure. These
include the presence and position of a facet for a pleural rib on the wall of the centrum posterior to the
parapophysis and the presence and shape of a mid-ventral fossa. In the Nemegt teleost, the rib articular
facet is located posterior to the parapophysis and the surface of the centrum is flat and has a long narrow
mid-ventral fossa. If the identification of the fish centrum found with R. kreigsteini as a posterior-precaudal
centrum from the Nemegt teleost is correct, it would have these features.
302
Acknowledgements
We are grateful to the 2006 KID Mongolian-Korea field party, especially Yuong-Nam LEE. We appreciate assistance
with collections, use of equipment, and lab space provided by Dave BOHASKA and Michael BRETT-SURMAN,
USNM, and Sam MCLEOD, Gary TAKEUCHI, and Vanessa RHUE of the LACM. Arvid AASE provided a speci-
men for examination from the FOBU collection. The manuscript greatly benefited from the comments of Gloria
ARRATIA. Postdoctoral funding for M.G.N. was provided by the Royal Tyrrell Museum Cooperating Society
and Natural Sciences and Engineering Research Council Discovery Grant A9180 (M.V.H. Wilson). Two travel
grants to visit the USNM and LACM were provided to M.G.N. by the Royal Tyrrell Museum Cooperating Soci-
ety. Doctoral funding and support for E.A.F, D.W.F, and H.N.W. was provided by the SANDS family, Damaris
WAGGONER, the HORNER Fund, the MSU Department of Cell Biology and Neuroscience, Jack HORNER, and
the Museum of the Rockies. This research was also supported by Korea-Mongolia International Dinosaur Project
funded by Hwaseong City (to D.A.W.).
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Authors’ addresses:
Michael G. NEWBREY: Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta T0J 0Y0, Canada
(current address); and Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9,
Canada; e-mail: mike.newbrey@gov.ab.ca
Donald B. BRINKMAN, Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta T0J 0Y0, Canada;
e-mail: don.brinkman@gov.ab.ca
Dale A. WINKLER, Department of Earth Sciences, Southern Methodist University, Dallas, Texas 75275-0395,
U.S.A.; e-mail: dwinkler@smu.edu
Elizabeth A. FREEDMAN, Museum of the Rockies, 600 W. Kagy Blvd, and Department of Earth Sciences, Montana
State University, Bozeman, MT 59717, U.S.A.; e-mail: eafreedman@gmail.com
Andrew G. NEUMAN, Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta T0J 0Y0, Canada;
e-mail: andrew.neuman@gov.ab.ca
Denver W. FOWLER, Museum of the Rockies, 600 W. Kagy Blvd, and Department of Earth Sciences, Montana
State University, Bozeman, MT 59717, U.S.A.; e-mail: df9465@yahoo.co.uk
Holly N. WOODWARD, Museum of the Rockies, 600 W. Kagy Blvd, and Department of Earth Sciences, Montana
State University, Bozeman, MT 59717, U.S.A.; e-mail: holly.n.woodward@gmail.com
304
ISBN 978-3-89937-159-8 www.pfeil-verlag.de
The Mesozoic was an important time in the evolution of chondrichthyan and
actino pterygian fi shes because it was then that most of the modern groups fi rst
entered the fossil record and began to radiate. By the end of the era, many archaic
forms had disappeared and the foundation had been laid for the modern diversity
of fi shes. Despite this signifi cant change, before 1990 there had been little concerted
research on Mesozoic fi shes and no synopsis or compilation of the systematics
and paleoecology of Mesozoic fi shes. To remedy this defi ciency, Gloria ARRATIA
organized the fi rst symposium, “Mesozoic Fishes – Systematics and Paleoecology”
in Eichstätt, Germany in 1993, and, with G. VIOHL, edited the fi rst volume in
the Mesozoic Fishes series. Published in 1996 included 36 papers about elasmo-
branchs, actinopterygians, sarcopterygians, and the paleoecology of certain impor-
tant fossil localities. Gloria ARRATIA and Hans-Peter SCHULTZE organized the
second symposium in Buckow, Germany in 1997, and edited the resulting volume
“Mesozoic Fishes 2 – Systematics and Fossil Record”, which included 31 papers.
Andrea TINTORI, Markus FELBER, and Heinz FURRER organized the third sym-
posium in Serpiano, near Monte San Giorgio, Switzerland in 2001. The results of
that symposium included 33 papers edited by G. ARRATIA and A. TINTORI and
published in “Mesozoic Fishes 3 – Systematics, Paleoenvironments and Biodiver-
sity”. Francisco POYATO-ARIZA organized the fourth symposium on “Mesozoic
Fishes – Systematics, Homology and Nomenclature” in Mirafl ores de la Sierra, near
Madrid, Spain, in 2005. The results of that symposium included 24 papers edited by
G. ARRATIA, H.-P. SCHULZE, and M. V. H. WILSON and published in “Mesozoic
Fishes 4 – Homology and Phylogeny”.
Rosario GOMEZ, Katia GONZALEZ-RODRIGUEZ, and Jesús ALVARADO-ORTE-
GA organized the fi fth and recent Symposium in the Museum del Desierto, Saltillo,
Coahuila, Mexico from August 2 to 7, 2010. The results presented in 22 research
papers, refl ect the current state of knowledge about Mesozoic Fishes, but represent
only a fraction of all contributions delivered during the meeting. Many of the oral
papers were about important preliminary research, yet to be revealed in the pub-
lished literature. The volume includes two main groups of fi shes, actinopterygians
(almost exclusively about teleosts) and sarcopterygians as well as papers dealing
with important assemblages of fossil fi shes of certain Mesozoic localities. Most of
the papers are solely dedicated to Mesozoic fossil fi shes, but some studies include
related fi shes up to the present, as well as papers dealing with specifi c morphological
aspects of actinopterygians, and homology problems. New discoveries are presented
about fi shes from Europe, North America, South America, Africa, and Australia.
The new discoveries and interpretations along with critical evaluation of previous
research collectively represent an exciting invitation and challenge to further research
on Mesozoic Fishes.
