A reassessment of the historical fossil findings from Bahia State Northeast Brazil reveals a diversified dinosaur fauna in the Lower Cretaceous of South America

Abstract

Supposed dinosaur remains were collected between 1859 and 1906 in the Lower Cretaceous Recôncavo Basin (Northeast Brazil). Since these materials remained undescribed, and most were considered lost. Recently, some of these historical specimens were rediscovered in the Natural History Museum of London, providing an opportunity to revisit them after 160 years. The specimens come from five different sites, corresponding to the Massacará (Berriasian-Barremian) and Ilhas (Valanginian-Barremian) groups. Identified bones comprise mainly isolated vertebral centra from ornithopods, sauropods, and theropods. Appendicular remains include a theropod pedal phalanx, humerus, and distal half of a left femur with elasmarian affinities. Despite their fragmentary nature, these specimens represent the earliest dinosaur bones discovered in South America, enhancing our understanding of the Cretaceous dinosaur faunas in Northeast Brazil. The dinosaur assemblage in the Recôncavo Basin resembles coeval units in Northeast Brazil, such as the Rio do Peixe Basin, where ornithopods coexist with sauropods and theropods. This study confirms the presence of ornithischian dinosaurs in Brazil based on osteological evidence, expanding their biogeographic and temporal range before the continental rifting between South America and Africa. Additionally, these findings reinforce the fossiliferous potential of Cretaceous deposits in Bahia State, which have been underexplored since their initial discoveries.

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Historical Biology
An International Journal of Paleobiology
ISSN: (Print) (Online) Journal homepage: www.tandfonline.com/journals/ghbi20
A reassessment of the historical fossil findings
from Bahia State (Northeast Brazil) reveals
a diversified dinosaur fauna in the Lower
Cretaceous of South America
Kamila L. N. Bandeira, Bruno A. Navarro, Rodrigo V. Pêgas, Natan S.
Brilhante, Arthur S. Brum, Lucy G. de Souza, Rafael C. da Silva & Valéria Gallo
To cite this article: Kamila L. N. Bandeira, Bruno A. Navarro, Rodrigo V. Pêgas, Natan S.
Brilhante, Arthur S. Brum, Lucy G. de Souza, Rafael C. da Silva & Valéria Gallo (11 Apr 2024):
A reassessment of the historical fossil findings from Bahia State (Northeast Brazil) reveals a
diversified dinosaur fauna in the Lower Cretaceous of South America, Historical Biology, DOI:
10.1080/08912963.2024.2318406
To link to this article: https://doi.org/10.1080/08912963.2024.2318406
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A reassessment of the historical fossil ndings from Bahia State (Northeast Brazil)
reveals a diversied dinosaur fauna in the Lower Cretaceous of South America
Kamila L. N. Bandeira
a
, Bruno A. Navarro
b
, Rodrigo V. Pêgas
c
, Natan S. Brilhante
c
, Arthur S. Brum
a,d
,
Lucy G. de Souza
e
, Rafael C. da Silva
f
and Valéria Gallo
a
a
Laboratório de Sistemática e Biogeografia, Departamento de Zoologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil;
b
Laboratório
de Herpetologia e Paleontologia, Museu de Zoologia - Universidade de São Paulo, São Paulo, SP, Brazil;
c
Laboratório de Paleontologia de Vertebrados
e Comportamento Animal, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil;
d
Laboratório de Sistemática e Tafonomia de Vertebrados
Fósseis, Departamento de Geologia e Paleontologia, Museu Nacional - Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil;
e
Faculdade
Estácio do Amazonas, Manaus, Amazonas, Brazil;
f
Museu de Ciências da Terra, Serviço Geológico do Brasil, Rio de Janeiro, RJ, Brazil
ABSTRACT
Supposed dinosaur remains were collected between 1859 and 1906 in the Lower Cretaceous Recôncavo
Basin (Northeast Brazil). Since these materials remained undescribed, and most were considered lost.
Recently, some of these historical specimens were rediscovered in the Natural History Museum of London,
providing an opportunity to revisit them after 160 years. The specimens come from ve dierent sites,
corresponding to the Massacará (Berriasian-Barremian) and Ilhas (Valanginian-Barremian) groups. Identied
bones comprise mainly isolated vertebral centra from ornithopods, sauropods, and theropods. Appendicular
remains include a theropod pedal phalanx, humerus, and distal half of a left femur with elasmarian anities.
Despite their fragmentary nature, these specimens represent the earliest dinosaur bones discovered in South
America, enhancing our understanding of the Cretaceous dinosaur faunas in Northeast Brazil. The dinosaur
assemblage in the Recôncavo Basin resembles coeval units in Northeast Brazil, such as the Rio do Peixe Basin,
where ornithopods coexist with sauropods and theropods. This study conrms the presence of ornithischian
dinosaurs in Brazil based on osteological evidence, expanding their biogeographic and temporal range
before the continental rifting between South America and Africa. Additionally, these ndings reinforce the
fossiliferous potential of Cretaceous deposits in Bahia State, which have been underexplored since their
initial discoveries.
ARTICLE HISTORY
Received 6 November 2023
Accepted 9 February 2024
KEYWORDS
Recôncavo Basin; Massacará
Group; Ilhas Group;
Ornithischia; Sauropoda;
Theropoda
Introduction
The Cretaceous strata in Brazil cover approximately 19% of its
territory (Schobbenhaus and Neves 2003; Da Silva et al. 2003) and
have yielded a noteworthy ichnological and osteological dinosaur
fossil record (Campos and Kellner 1991; Kellner and Campos 1999,
2000; Bittencourt and Langer 2011). The main dinosaur-bearing
localities come from Lower Cretaceous deposits, especially in the
Northeast region of the country (Figure 1; see also Supplementary
Data). The dinosaur components are mainly represented by rebba-
chisaurids (Lindoso et al. 2019) and titanosaurian sauropods (Zaher
et al. 2011; Ghilardi et al. 2016; Carvalho et al. 2017), associated
with abelisauroid (Zaher et al. 2020; De Souza et al. 2021), spino-
saurid (Kellner and Campos 1996; Sues et al. 2002, França et al.
2022; Lacerda et al. 2023), carcharodontosaurid (Medeiros et al.
2014, 2019; Pereira et al. 2020), megaraptoran (Aranciaga-Rolando
et al. 2018), and coelurosaurian theropods (Kellner 1999; Naish
et al. 2004; Sayão et al. 2020), including avialans (Carvalho et al.
2015, 2021).
Regarding the ornithischian record, the occurrences are scarce
and most of them doubtful. They include putative iguanodontian
centra coming from the Recôncavo Basin (Mawson and Woodward
1907), an ornithischian ischium (MN 7021-V) – later reinterpreted
as a spinosaurid rib (Leonardi and Borgomanero 1981; Machado
and Kellner 2007)—, and a partial preserved caudal vertebra
(UFMA 1.10.240) from the Alcântara Formation (Medeiros and
Schultz 2002; Medeiros et al. 2007), which was briefly described
and assigned to cf. Ouranosaurus by Novas (2009). In contrast, the
ichnological record concerning this group is abundant and wide-
spread amongst the Brazilian Lower Cretaceous deposits, mainly in
the small half-grabens of the Rio do Peixe and Iguatu basins. This
record includes ichnites of putative thyreophorans, small-to-
medium-sized bipedal and graviportal ornithopod trackmakers
(Leonardi 1994; Leonardi and Carvalho 2002, 2021).
Although most of these dinosaur-bearing units have been exten-
sively explored over the last decades, the dinosaur components of
the Recôncavo Basin units remain poorly understood. Most of the
data regarding the Recôncavo Basin dinosaurs come from historical
publications older than a century ago (e.g. Allport 1860; Marsh
1869; Woodward 1888; Mawson and Woodward 1907). In addition,
most of these materials are considered lost by subsequent works
(e.g. Kellner and Campos 2000). Although some re-evaluations of
other archosaurs from the Recôncavo Basin have been performed in
recent years (e.g. Rodrigues and Kellner 2010; Souza et al. 2015,
2019), the putative dinosaur material remained undescribed in
detail, with few mentions of these specimens in the literature (e.g.
Bittencourt and Langer 2011).
Notwithstanding, some of these historical materials were
recently located in the palaeontological collection of the Natural
CONTACT Kamila L. N. Bandeira kamilabandeira@yahoo.com.br Laboratório de Sistemática e Biogeografia, Departamento de Zoologia, Universidade do Estado do
Rio de Janeiro, Rua São Francisco Xavier 524, Rio de Janeiro, RJ 20550-013, Brazil
Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2024.2318406
HISTORICAL BIOLOGY
https://doi.org/10.1080/08912963.2024.2318406
© 2024 Informa UK Limited, trading as Taylor & Francis Group
Published online 11 Apr 2024

History Museum of London (NHM) and are presented herein. The
specimens described below represent the first dinosaur bones col-
lected in South America (e.g. Allport 1860) and revealed
a diversified dinosaur fauna in the Recôncavo Basin. This historical
dinosaur bones enhance our understanding about the faunal suc-
cession in Gondwana during the earliest Cretaceous. Furthermore,
this work aims to encourage Brazilian palaeontologists to conduct
further fieldwork in the basins of Bahia State, as they represent one
of the earliest Cretaceous faunas in South America and indicates
potential new important discoveries (e.g. Souza and Campos 2018).
Historical background and geological settings
The Recôncavo Basin is a NW – SE-oriented half-graben located in
Bahia State, covering approximately 12.000 km
2
and reaching about
10 km of maximum thickness (Prates and Fernandez 2015). The
basement of this basin is composed of Neoproterozoic rocks from
the São Francisco Craton, characterised by a network of high-dip
synthetic normal faults divided into three structural blocks: Low,
High, and Platform (Destro et al. 2003). The depositional history of
the Recôncavo Basin can be separated into five phases: a syneclysis
stage in the Permian, a pre-rift stage during the Tithonian to Early
Berriasian (Dom João Local Age), a syn-rift stage starting in the
Early Berriasian and extending to the Early Aptian (Rio da Serra,
Aratu, Buracica, and Jiquiá local ages), and a post-rift stage ranging
from the Late Aptian to Early Albian (Alagoas Local Age), later
covered by Neogene (Miocene and Pliocene) and Quaternary
deposits (Viana et al. 1971). The syn-rift sequence of the
Recôncavo Basin is commonly referred in the literature as the
‘Bahia Supergroup’, which comprises the Santo Amaro Group
(Itaparica, Água Grande, Candeias and Maracangalha formations),
the Ilhas Group (Marfim, Pojuca and Taquipe formations), the
Massacará Group (Salvador and São Sebastião formations), and
the Marizal Formation (Caixeta et al. 1994).
According to Da Silva et al. (2007), the beginning of the syn-rift
phase resulted in the formation of several tectonic lakes with differ-
ential subsidence, represented by the Candeias and Maracangalha
formations. The Tauá and Gomo members (Candeias Formation) are
deposited under lacustrine conditions, characterised by clays rich in
organic matter. They are associated with gravitational flows and
fluvial system tracts of the Pitanga and Caruaçu members
(Maracangalha Formation), which are related to the reactivation of
transcurrent faults. By contrast, the Ilhas Group encompasses
a prograding deltaic paleoenvironment, based on the succession of
sandstones and shales (e.g. Marfim Formation), as well as mudstones
and limestones (e.g. Pojuca Formation). The Catu Member (Marfim
Formation) indicates several changes in the development of lacus-
trine systems. The high relief formed by the Salvador Fault on the
eastern margin gradually intruded flagstones and conglomeratic
sandstone facies of the Sesmaria Member (Salvador Formation)
into these tectonic lakes. The establishment of the prograding deltaic
system of the Pojuca Formation indicates episodic marine incursions
(Santiago Member) that supplied these tectonic lakes. A subsidence
decrease, which probably occurred during the Early Aptian (Arai
2014; but see also Assine et al. 2016; Parméra et al. 2019), progres-
sively silted up these lacustrine systems with fluvial sediments from
the São Sebastião Formation. In the western part of the basin, erosive
processes on the Ilhas Group developed a canyon system that is filled
by the alluvial fans deposits of the Taquipe Formation. The post-rift
phase, represented by the Marizal Formation, was deposited through
the formation of alluvial and delta fans.
The deposits of Recôncavo Basin hold a relatively diversified fossil
record, including microfossils (e.g. foraminifera, ostracods, and ‘con-
chostraceans’), molluscs (e.g. bivalves and gastropods), and plant
remains, such as palynomorphs, amber, and silicified conifer logs
(Milhomem et al. 2003). Vertebrate remains are represented by cepha-
lic fins of hybodontiform sharks (Acrodus nitidus Woodward 1888),
several occurrences of actinopterygians (e.g. Ellimmichthys longicosta-
tus (Cope 1886); ‘Lepidotes’ mawsoni Woodward 1888) and sarcopter-
ygians (e.g. Mawsonia gigas Mawson and Woodward 1907), remains of
chelonians and putative plesiosaurians (Marsh 1869; Woodward
1891), some crocodilian teeth and bones (e.g. ‘Thoracosaurus bahiaen-
sis’, Sarcosuchus hartti; Souza et al. 2015; Souza 2019), pterosaurian
teeth (Woodward 1891; Rodrigues and Kellner 2010), and supposed
dinosaur specimens (Allport 1860; Hartt 1870; Mawson and
Woodward 1907; Figueiredo and Gallo 2021).
The outcrops from which the historical material was collected are
recognised by some studies as belonging to the ‘Bahia Supergroup’, but
without an assignment to a specific horizon (e.g. Rodrigues and Kellner
2010; Bittencourt and Langer 2011). Hartt (1870) and Hartt and
Agassiz (1875) regarded these deposits as potentially equivalent to
the ‘Neocomian’ strata of Europe. Later, Derby (1878) assigned the
entire coastal basin from Bahia into the Lower Cretaceous. More
recently, Souza et al. (2015) suggested that these historical localities
probably belong to the Late Valanginian to Early Barremian Ilhas
Group (Caixeta et al. 1994). However, given the high urbanisation of
the Salvador area and the absence of a refined stratigraphic control
during the collection of these materials, Souza et al. (2019) suggested
some cautiousness to assign such rocks to any more specific unit
and age.
Nevertheless, we bring here some novelties based on the descrip-
tions of NHM collection labels, in which explain the specific litho-
facies that each specimen recovered and allowing a more refined
horizon assignment. According to the collection labels, the specimens
reviewed here were recovered from five different localities through
field seasons from 1859 to 1906 (Table 1). The outcrops were first
described by Allport (1860) and later explored by Mawson, in which
compiled them into a detailed map in Mawson and Woodward
(1907). We evaluated these sites and compared the data of collection
labels within stratigraphic studies of the Recôncavo Basin (e.g. Da
Silva et al. 2007), plotting them at the ‘Carta Geológica do Brasil ao
Milionésimo’ (Souza et al. 2004). The revised map (Figure 2) shows
that the prospected localities match with the outcrops of the Ilhas
Group and the Salvador Formation, correlating with the specific
lithofacies in which the specimens were found (Figure 3).
Institutional abbreviations
CPPLIP, Centro de Pesquisas Paleontológicas Llewellyn Ivor Price,
Peirópolis, Brazil; GSI, Geological Survey of India, Kolkata, India;
IRSNB, MACN, Museo Argentino de Ciencias Naturales
‘Bernadino Rivadavia’, Buenos Aires, Argentina; MCF-PVPH,
Museo ‘Carmen Funes’ - Paleontología de Vertebrados Plaza
Huincul, Plaza Huincul, Argentina; Museo de La Plata, La Plata,
Argentina; MN, Museu Nacional, Universidade Federal do Rio de
Janeiro, Rio de Janeiro, Brazil; MPM, Museo Regional Provincial
‘Padre Jesús Molina’, Río Gallegos, Argentina; MUCPv, Museo de la
Universidad Nacional del Comahue, Neuquén, Argentina; NHM,
Natural History Museum, London, United Kingdom; SGB, Serviço
Geológico Brasileiro, Rio de Janeiro, Brazil; SHN, Sociedade de
História Natural, Torres Vedras, Portugal; UFMA, Universidade
Federal do Maranhão, São Luís, Brazil; UFRJ, Universidade Federal
2KAMILA L.N. BANDEIRA ET AL.

Figure 1. Cretaceous deposits from Brazil and their dinosaur assemblages, emphasising occurrences from the Lower Cretaceous units. 1–3, Botucatu Formation (Paraná
Basin); 4–5, Goio Erê and Rio Paraná formations (Caiuá Group); 6–8, Abaeté, Quiricó, and Três Barras formations (Sanfranciscana Basin); 9–10, Maceió and Feliz Deserto
formations (Sergipe-Alagoas Basin); 11, Antenor Navarro, Sousa, and Rio Piranhas formations (Rio do Peixe basins); 12, Quixoá (Icó) and Malhada Vermelha formations
(Iguatu basins); 13, Rio da Batateira, Crato, and Romualdo formations (Araripe Basin); 14, Açu Formation (Potiguar Basin); 15, Itapecuru Formation (Parnaíba Basin); 16,
Alcântara Formation (São Luís-Grajaú Basin). The asterisk exhibits the occurrences from the Recôncavo Basin presented by this work. Detailed information on each
occurrence is provided in the Supporting Information (File S1). Modified from ‘Carta Geológica do Brasil ao Milionésimo’ (Souza et al. 2004).
HISTORICAL BIOLOGY 3

Table 1. Collection details of the specimens described in this work.
Specimen Material Collector Year Facies Locality described in the collection label Unit assigned
NHM PV R.2459 Dorsal centrum Samuel Allport 1859 Sandy shale Fort Montserrate (= Forte Monte Serrat). Marfim Formation
NHM PV R.2129 (a) Caudal centrum Joseph Mawson 1894 Mudstones Beach near Itacaranha. Pojuca Formation
NHM PV R.2129 (b) Caudal centrum Joseph Mawson 1894 Sandy shale Beach near Itacaranha. Marfim Formation
NHM PV R.2980 Caudal centrum Joseph Mawson 1897–1900 Sandy shale
and sandstones
Beach between Plataforma and Itacaranha,
Pedra Furada Bay.
Marfim Formation
NHM PV R.2981 (a) Dorsal centrum Joseph Mawson 1897–1900 Sandy shale
and sandstones
Beach between Plataforma and Itacaranha,
Pedra Furada Bay.
Marfim Formation
NHM PV R.2981 (b) Caudal centrum Joseph Mawson 1897–1900 Sandy shale
and sandstones
Beach between Plataforma and Itacaranha,
Pedra Furada Bay.
Marfim Formation
NHM PV R.2982 Pedal phalanx Joseph Mawson 1897–1900 Sandy shale
and sandstones
Beach between Plataforma and Itacaranha,
Pedra Furada Bay.
Marfim Formation
NHM PV R.3424 Distal end of a femur Joseph Mawson 1906 Shales Beach near Plataforma Station,
Bahia-São Francisco Railway Km 6
Marfim Formation
NHM PV R.3425 Dorsal centrum Joseph Mawson 1906 Shales Bahia, Brazil.* Marfim Formation
NHM PV R.3429 Caudal centrum Joseph Mawson 1906 Shales Beach near Plataforma Station,
Bahia-São Francisco Railway Km 6
Marfim Formation
NHM PV R.3426 Caudal centrum Joseph Mawson 1906 Flagstones and
conglomerates
Mapelle Quarry, São Francisco Railway, Km 23 Salvador Formation
NHM PV R.3427 Partial caudal centrum Joseph Mawson 1906 Flagstones and
conglomerates
Mapelle Quarry, São Francisco Railway, Km 23 Salvador Formation
NHM PV R.3428 (1 and 2) Two caudal centra Joseph Mawson 1906 Flagstones and
conglomerates
Mapelle Quarry, São Francisco Railway, Km 23 Salvador Formation
MN 4451/1-V Probable humeral diaphysis Joseph Mawson 1906? Flagstones and
conglomerates
Mapelle Quarry, São Francisco Railway, Km 23 Salvador Formation
Number unknown Partial sauropod teeth crowns Joseph Mawson Unknown Flagstones and
conglomerates
Mapelle Quarry, São Francisco Railway, Km 23 Salvador Formation
*The material probably was found on the beach near Plataforma Station (Bahia-São Francisco Railway Km 6), given the taphonomical similarities with other specimens found in this locality and due to both were collected in the
same year.
4KAMILA L.N. BANDEIRA ET AL.

do Rio de Janeiro, Rio de Janeiro, Brazil; UNPSJB, Universidad
Nacional de la Patagonia San Juan Bosco, Comodoro Rivadavia,
Argentina. CPPLIP, Centro de Pesquisas Paleontológicas Llewellyn
Ivor Price, Peirópolis, Brazil; GSI, Geological Survey of India,
Kolkata, India; IRSNB, MACN, Museo Argentino de Ciencias
Naturales ‘Bernadino Rivadavia’, Buenos Aires, Argentina; MCF-
PVPH, Museo ‘Carmen Funes’ - Paleontología de Vertebrados
Plaza Huincul, Plaza Huincul, Argentina; MLP, Museo de La Plata,
La Plata, Argentina; MN, Museu Nacional, Universidade Federal do
Rio de Janeiro, Rio de Janeiro, Brazil; MPM, Museo Regional
Provincial ‘Padre Jesús Molina’, Río Gallegos, Argentina; MUCPv,
Museo de la Universidad Nacional del Comahue, Neuquén,
Argentina; NHM, Natural History Museum, London, United
Kingdom; SGB, Serviço Geológico Brasileiro, Rio de Janeiro, Brazil;
SHN, Sociedade de História Natural, Torres Vedras, Portugal;
UFMA, Universidade Federal do Maranhão, São Luís, Brazil;
UFRJ, Universidade Federal do Rio de Janeiro, Rio de Janeiro,
Brazil; UNPSJB, Universidad Nacional de la Patagonia San Juan
Bosco, Comodoro Rivadavia, Argentina.
Systematic Palaeontology
Dinosauria Owen 1842
Ornithischia Seeley 1888
Genasauria Sereno 1986
Neornithischia Cooper 1985
Cerapoda Sereno 1986
Ornithopoda Marsh 1881
Elasmaria Calvo et al. 2007
Tietasaura gen. nov.
urn: lsid:zoobank.org:act:814725BB-A522-465F-975D-
1755A11C3956
Etymology
The generic epithet is a combination of Tieta (nickname for
Antonieta in Portuguese) and -saura (σαύρα), the genitive form of
-saurus and meaning lizard in ancient Greek. The name Tieta
honours the main character from the homonymous novel ‘Tieta
do Agreste’ by the famous author Jorge Amado, who was born in
Figure 2. Historical fossil-bearing localities of the Lower Cretaceous Recôncavo Basin in Northeast Brazil, modified from Allport (1860) and Mawson and Woodward (1907).
Localities which have yielded dinosaur remains are described in Table 1. Geographic range of the geological units was taken from ‘Carta Geológica do Brasil ao Milionésimo’
(Souza et al. 2004). Scale bar = 25 km.
HISTORICAL BIOLOGY 5

Bahia and lived in Salvador City. The name Antonieta further
means ‘priceless’, alluding to the value of Tietasaura derbyiana sp.
nov. as the first nominal ornithischian species from Brazil.
Type species
Tietasaura derbyiana sp. nov.
Diagnosis
As for type and only known species, by monotypy.
Tietasaura derbyiana sp. nov.
(Figure 4; Table S3)
urn: lsid:zoobank.org:act:52683BA8-C4C5-4A81-90 DB-
3BC6431946D2
Etymology
The specific epithet is an eponym honouring Orville A. Derby
(1851–1915), founder and the first director from Brazilian
Mineralogical and Geological Commission (Serviço Geológico
e Mineralógico do Brasil, nowadays SGB), being also the former
director of the National Museum of Rio de Janeiro (MN) and one of
the pioneers of palaeontology in the Recôncavo Basin. Despite all
tragedies in his life and the blatant lack of governmental support,
Derby valiantly fought for the scientific progress of the Brazilian
geosciences.
Holotype
NHM-PV R.3424, represented by a distal half of a small left femur.
Diagnosis
Small sized elasmarian ornithopod exhibiting an unique combina-
tion of character states on the femur (putative autapomorphies
marked with an asterisk): presence of a marked anterior linea
muscularis followed by several longitudinal striae converging dis-
tally towards the intercondylar extensor groove; broad but shallow
intercondylar extensor groove; stout supracondylar ridges that
extends medially; fibular supracondylar ridge sinuous and bearing
a lateral fossa*; hemispherical distal femoral condyles in the poster-
ior view, being the tibial condyle twice as large as fibular condyle;
distinct prominent crest in the median margin of the tibial con-
dyle*; fibular condyle with straight lateral margin and continuous in
the distal view, lacking an indentation formed by a condyloid
(rectangular) process; presence of an offset condylid, medial to
the fibular condyle; broad and deep intercondylar flexor fossa,
subtriangular in shape and much extending into the diaphysis.
Type locality and horizon
The holotype of Tietasaura derbyiana was recovered at a beach near
the Plataforma Station (Locality 3), Salvador City, Bahia State. The
shale facies outcropping in this locality are associated with the
Valanginian – Hauterivian Marfim Formation (Ilhas Group,
Recôncavo Basin).
Description and comparisons
Tietasaura derbyiana comprise a moderately preserved distal end of
a small left femur (231.09 mm in preserved length; see Table S3),
with less than a half of its total proximodistal length. This specimen
was designated as a Hyposaurus sp. in the collection labels of the
NHM, a dyrosaurid crocodyliform genus present in the Upper
Figure 3. Stratigraphic chart of the Lower Cretaceous Massacará and Ilhas groups (Recôncavo Basin), highlighting their vertebrate assemblages (coloured boxes).
1, hybodontiforms (Acrodus nitidus); 2, semionotids (‘Lepidotes’ spp.); 3, mawsoniids (Mawsonia gigas); 4, undetermined testudines; 5, pholidosaurids (Sarcosuchus
hartti); 6, putative gavialoids (‘Thoracosaurus bahiaensis’); 7, pterosaurs (anhanguerids); 8, elasmarians (Tietasaura derbyiana gen. et sp. nov.); 9, iguanodontians;
10, diplodocoids; 11, spinosaurids; 12, carcharodontosaurians; 13, undetermined small theropods (tyrannosauroids?); 14, titanosaurs (lithostrotians); 15, amiids
(Calamopleurus mawsoni); 16, cladocyclids (Cladocyclus mawsoni); 17, aspidorhynchids (‘Belonostomus’ carinatus); 18, undetermined clupeomorphs
(Scrombroclupeoides scutata); 19, ellimmichthyiforms (Ellimmichthys longicostatum, Ellimmichthys spinosus, Scutatuspinosus itapagipensis). References regarding
the vertebrate occurrences were taken through bibliographic survey (see text). Geological chart modified from Da Silva et al. (2007). Silhouettes from several
sources.
6KAMILA L.N. BANDEIRA ET AL.

Cretaceous to Early Paleocene strata of North America, North
Africa, and Brazil (e.g. Veloso et al. 2023). Here, however, we
reinterpret it as belonging to an elasmarian ornithopod based on
several characteristics (see below). When compared with crocodyli-
form femora, remarkable anatomical distinctions are observable in
Tietasaura derbyiana. In the anterior view, for example, the femur
NHM-PV R.3424 exhibits a slightly convex surface towards the
distal portion, with the extensor groove more developed on the
distal surface than the anterior one. By contrast, in
Coelognathosuchia taxa (Goniopholidae+Tethysuchia sensu
Martin et al. 2014), such as Burkesuchus mallingrandensis (see
Novas et al. 2021, fig. 5) and Anteophthalmosuchus hooleyi
(Martin et al. 2016, fig. 16), Hyposaurus rogersii (Pellegrini et al.
2021, fig. 1), and an unnamed dyrosaurid from Senegal (Martin
et al. 2019, fig. 6), the extensor groove is broad and extends proxi-
mally in the diaphysis. In the posterior view, Tietasaura derbyiana
has a remarkably deep and broad flexor fossa, whereas in coelog-
nathosuchians this region is more restricted, developing as
a vertical groove. Additionally, the fibular condyle in coelognatho-
suchians is much more developed distally than the tibial one, con-
trasting with the inverse pattern observed in Tietasaura derbyiana.
Finally, in the distal view, the femoral epiphysis of Tietasaura
derbyiana is wider mediolaterally, while in crocodyliform femora
it develops anteroposteriorly.
Although the bone exhibits signs of pre-burial transportation, its
surface is well preserved, and the periosteum preserves several
muscular striae and rugosities. Moreover, the diaphysis in
Tietasaura derbyiana shows a spiral fracture (Figure 4A,B) typical
of fresh bone breakage (e.g. Galloway 1999). In the median portion
of the diaphyseal surface, the periosteum is well-preserved and
particularly smooth. This feature could be interpreted as an indi-
cator of osteological maturity, contrasting with the long-grained or
dimpled patterns seen in immature specimens of pterosaurs
(Bennett 1993), ceratopsians (Tumarkin‐Deratzian 2009), and
birds (Tumarkin-Deratzian et al. 2006). Comparing with other
dinosauromorphs, the bone cortex thickness in NHM-PV R.3424
further indicates that the individual reached its asymptotic mass
(Sander and Tückmantel 2003; Griffin et al. 2019). However, due to
the unavailability of paleohistological or CT-scan data for this
individual, a precise ontogenetic assessment for Tietasaura derbyi-
ana cannot be assumed. Therefore, such inferences are considered
tentative and should be approached with caution (see Griffin et al.
2021 for an overview).
The diaphysis, as preserved, is swelled towards the distal end
surface in anterior and posterior views (Figure 4A–C). In the lateral
and medial views, the preserved shaft exhibits an accentuated
posterior curvature, indicating a sigmoid profile for the femur
(Figure 4B–D). This feature is widely distributed, being present in
some early-diverging ornithischians, such as Eocursor parvus Butler
et al. 2007 and Pisanosaurus mertii Casamiquela 1967 (see Butler
2010; Agnolín and Rozadilla 2018), thescelosaurids (Gilmore 1915;
Scheetz 1999; Boyd et al. 2009; Brown et al. 2011, 2013), and some
elasmarians, such as Anabisetia saldiviai Coria and Calvo 2002.
The anterior surface in Tietasaura derbyiana is almost planar,
except for a shallow ‘V-shaped’ intercondylar extensor groove that
does not reach the fibular and tibial condyles in the distal view
Figure 4. Holotypic distal half of the left femur of Tietasaura derbyiana gen. et. sp. nov. (NHM-PV R.3424) from the Valanginian–Hauterivian Marfim Formation (Ilhas Group)
at Plataforma Station (Locality 3). A, anterior; B, medial; C, posterior; D, lateral; E, distal views. Anatomical abbreviations: ali, anterior linea muscularis; cd, condylid process;
cr, crest; fc, fibular condyle; gr, groove; ieg, intracondylar extensor groove; iff, intracondylar flexor fossa; lfs, lateral fossa; rg, rugosity; sc, sulcus; sf, spiral fracture; scr,
supracondylar ridge; st, striae; tc, tibial condyle. Scale bar = 100 mm.
HISTORICAL BIOLOGY 7

(Figure 4E). This condition differs from the condition observed in
most theropods, in which this region presents a deep and elongated
groove (Carrano et al. 2012). This condition resembles the mor-
phology found in thescelosaurids and ornithopods (e.g.
Krumenacker 2017; Madzia et al. 2018). In addition, the anterior
surface exhibits remarkable anterior linea intermuscularis and sev-
eral striae, which could be associated with M. femorotibialis. Both
condyles are visible in the anterior view, being the tibial more
bevelled and extending further distally than the fibular one, but
not reaching the diaphyseal portion of the distal end (Figure 4A–E).
In the posterior view (Figure 4C), the tibial condyle is much larger
than the fibular one, but both are broad and hemispherical in shape. In
lateral and medial views (Figure 4B–D), a pair of prominent supra-
condylar ridges are present, enclosing a fully opened, deep posterior
intercondylar flexor fossa. This fossa is vertically developed and tapers
towards the diaphysis acquiring a ‘V-shaped’ aspect. In the fibular
condyle, the supracondylar ridge acquires a sinuous profile in the
posterior view (Figure 4C). In contrast, the supracondylar ridge is
confluent and merges with the condyle in the lateral view
(Figure 4D). The tibial condyle is slightly oblique, posteromedially
inclined, with a round lateral aspect. In distal view (Figure 4E), the
fibular condyle has a straight and continuous lateral margin, lacking an
indentation that detaches a condyloid process parasagittal to the
femoral shaft (Figure 5E–G). In contrast, medially to the fibular con-
dyle, a small accessory condylid is present, as in Notohypsilophodon
comodorensis Martínez 1998 (Figure 5A–C).
In lateral view, the strongly sigmoidal shaft of Tietasaura derbyiana
differs from the condition seen in Hypsilophodon foxii Huxley 1870,
some elasmarians (e.g. Gasparinisaura cincosaltensis Coria and Salgado
1996a, Talenkauen santacrucensis Novas et al. 2004, iguanodontians,
and theropods, such as noasaurids and maniraptorans, in which the
femora display relatively straighter profiles (e.g. Hulke 1882; Madzia
Figure 5. Schematic draw comparing selected elasmarian femora in (1) posterior and (2) distal views. A, Tietasaura derbyiana gen. et. sp. nov. (NHM-PV R.3424);
B, Notohypsilophodon comodorensis (UNPSJB-Pv 942); C, Gasparinisaura cincosaltensis (MUCPv-208); D, Fulgurotherium australe (NHM-PV R.3719); E, Trinisaura santamar-
tensis (MLP 08-III-1-1); F, Morrosaurus antarcticus (MACN-Pv 197); G, Isasicursor santacrucensis (MPM 21,533); H, Anabisetia saldiviai (MCF-PVPH 74). Red arrows exhibit the
taxa that exhibits a distinct condylid processes between the condyles, while the blue arrows indicate the development and shifting of the condyloid (‘rectangular’)
processes. Dotted lines highlight different patterns on general shape (convex or almost rectilinear) and condyle development of femoral surfaces in the posterior (1) and
distal (2) views. Anatomical abbreviations: id, indentation; ieg, intracondylar extensor groove. Without scale for comparative purposes.
8KAMILA L.N. BANDEIRA ET AL.

et al. 2018; Rozadilla et al. 2019). However, it is remarkable that the
femur shaft is slightly sigmoid in perinate specimens of Iguanodon
galvensis Verdú et al. 2015 but acquires a fully straight profile through
its ontogenetic development.
Compared with theropods, the new species lacks any sign of an
anteromedial crest (Carrano and Sampson 2008). The fibular supra-
condylar crest confluent with the condyle also contrasts with what is
observed in theropods, in which this crest is posteriorly projected and
detached from this condyle (e.g. Carrano 2007; Gianechini and
Apesteguia 2011; Egli et al. 2016; Rauhut and Carrano 2016; Novas
et al. 2018). In paravians, excepting dromaeosaurids, the articular
regions are separated by a deep groove, forming a trochlea-like articu-
lar surface in distal view (Baumel and Witmer 1993; Chiappe 1996;
Norell and Makovicky 1997; Forster et al. 1998).
The mostly planar anterior surface of Tietasaura derbyiana further
differs from the condition observed in most theropods, in which this
region presents a deep and elongated anterior intercondylar groove
(Carrano et al. 2012). In this respect, Tietasaura derbyiana is similar to
the morphology found in thescelosaurids and ornithopods (e.g.
Krumenacker 2017).
Tietasaura derbyiana differs from iguanodontians in lacking a
medially inflated medial condyle that partially covers the posterior
intercondylar groove (e.g. Madzia et al. 2018). It also differs from
most ornithopods in lack of mediolaterally compressed distal con-
dyles in the posterior view. As in elasmarians, the condyles in
Tietasaura derbyiana are often subcircular, as seen in
Kangnasaurus coetzeei Haughton 1915 (Cooper 1985),
Gasparinisaura cincosaltensis, Anabisetia saldiviai, Trinisaura san-
tamartaensis Coria et al. 2013, Notophysilophodon comodoriensis,
and Morrosaurus antarcticus Rozadilla et al. 2016.
Tietasaura derbyiana is further distinguished from most neor-
nithischians by the absence of an indentation on the posterolateral
edge of the femur in distal view, between the main corpus of the
fibular condyle and the condyloid (or rectangular) process, as seen
in iguanodontians (e.g. Galton 1977; Forster 1990; Bertozzo et al.
2017; Maidment et al. 2022), Burianosaurus augustai Madzia et al.
2018, some elasmarians such as Kangnasaurus coetzeei, Anabisetia
saldiviai, Trinisaura santamartaensis, and Morrosaurus
antarcticus, thescelosaurids (e.g. Barta and Norell 2021; Sues
et al. 2023), and, although quite gentle, basal marginocephalians
(e.g. Butler and Zhao 2009; Han et al. 2018). Tietasaura derbyiana
lacks this indentation (thus lacking a distinct rectangular/condy-
loid process) and thus exhibits a straight medial edge of the fibular
condyle in distal view. In this respect, Tietasaura derbyiana is like
some elasmarians, such as Fulgurotherium australe Huene von
1932 (e.g. Molnar and Galton 1986), Gasparinisaura cincosalten-
sis, Notohypsilophodon comodoriensis, Isasicursor santacrucensis
Novas et al. 2019, and the Victorian femur type I (Rich and Rich
1989). Within elasmarians, Tietasaura derbyiana resembles
Notohypsilophodon comodorensis in the conspicuously sharp pos-
terior supracondylar ridges (Ibiricu et al. 2010), as well as the
presence of a condylid between both condyles. The fibular condyle
of Tietasaura derbyiana is also strikingly like that of
Gasparinisaura cincosaltensis, roughly in the shape of
a rectangular triangle with a slightly rounded medial edge in the
distal view.
Ornithopoda Marsh 1881
Iguanodontia Baur 1891
Ankylopollexia Sereno 1986
Styracosterna Sereno 1986
Gen. et sp. indet.
Specimen A
Referred material
NHM-PV R.3425, represented by an isolated middle dorsal cen-
trum (Figure 6; Table S2).
Locality and horizon
In contrast to the other materials studied here, the collection label
of NHM-PV R.3425 only contains the description ‘Cretaceous.
Bahia, Brazil’. in the provenance data, hindering major details
about the exact locality that the specimen came. Nonetheless,
according to the site descriptions provided by Mawson and
Figure 6. NHM-PV R.3425, isolated middle dorsal centrum with iguanodontian affinities (Specimen A) from the Valanginian–Hauterivian Marfim Formation (Ilhas Group) at
Plataforma Station (Locality 3). A, right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views. Anatomical abbreviations: avh, anteroventral heel; ct, cotyle;
nvf, neurovascular foramina; mco, median concavity; ncj, neurocentral joint; pas, posterior articulation surface; pvg, posteroventral groove. Scale bar = 100 mm.
HISTORICAL BIOLOGY 9

Woodward (1907), we can safely ascribe this specimen to the Ilhas
Group (Valanginian – Barremian). The specimen NHM-PV R.3425
might have been recovered from some outcrop at the beach near the
Plataforma Station (Locality 3; see Table 1), based on taphonomical
features of the specimen, such as the colour and the abrasion
degree. The year in which this specimen was collected (1906) also
supports this assumption, wherein only three other similar materi-
als were reported from this locality.
Description and comparisons
NHM-PV R.3425 is referred to a middle dorsal centrum given the
absence of articular facets of chevrons. The centrum is dorsoventrally
taller than anteroposteriorly long, as in some middle dorsal centra of
Iguanodon bernissartensis Boulenger 1881, Mantellisaurus atherfiel-
densis (Hooley 1925), Hippodraco scutodens, Iguanacolossus fortis
McDonald et al. 2010, and Morelladon beltrani Gasulla et al. 2015
(see Norman 1980, 1986; McDonald et al. 2012). Both anterodorsal
and anteroventral corners of the anterior articular surface surpass the
posteroventral one (Figure 6A,B). In addition, the anteroventral
expansion creates a rounded anteroventral heel that is slightly
deflected anteriorly. The centrum exhibits an opisthoplatyan inter-
central articulation, bearing a gently concave anterior surface and an
almost flat posterior surface that exhibits ellipsoid outlines
(Figure 6E,F). Signals of lateral striations circumscribing the articular
surfaces are absent but could correspond to a taphonomic artefact
since this facet is well abraded. In the lateral view, the posterior
articular surface displays subparallel margins, which slightly diverges
dorsally. The lateral surfaces of NHM-PV R.3425 exhibit a series of
small neurovascular foramina, mainly on the right surface. A marked
neurocentral joint is observable on the dorsal surface, indicating that
NHM-PV R.3425 could correspond to an immature individual
(Figure 6C). The ventral margin is gently concave in lateral view
(Figure 6A,B). A marked posteroventral groove is present ventrally,
lacking crests or ridges (Figure 6D).
The centrum is slightly constricted medially and has an ‘hour-
glass shape’ in both dorsal and ventral views (Figure 6C,D), which is
the typical morphology observed in ornithischian dorsal centra (e.g.
Norman et al. 2004a). NHM-PV R.3425 differs from thyreophorans
(e.g. Raven et al. 2020; Breeden et al. 2021) and marginocephalians
(e.g. Butler and Zhao 2009) in exhibiting taller than wide articular
centra, with a posteroventral margin deeper than the anteroventral
one in lateral view. These features ally NHM-PV R.3425 to some
iguanodontian ornithopods, such as Iguanodon bernissartensis
Boulenger 1881, Mantellisaurus atherfieldensis (Hooley 1925),
Hippodraco scutodens McDonald et al. 2010, and Iguanacolossus
fortis McDonald et al. 2010. Another typical ornithopod feature that
can be seen in NHM-PV R.3425 corresponds to a series of small
neurovascular foramina on the lateral surface of the centra, like
what is seen in elasmarians (e.g. Calvo et al. 2007; Rozadilla et al.
2019), Sektensaurus sanjuanboscoi Ibiricu et al. 2019, and iguano-
dontians (e.g. Wang et al. 2010), including hadrosaurids (e.g.
Cruzado-Caballero 2017).
The lack of the median ventral keel in NHM-PV R.3425 differ it
from the middle dorsal centra of several ornithischians such as
Hypsilophodon foxii (see Hulke 1882), Psittacosaurus mongoliensis
(Osborn 1923) (see Sereno and Chao 1988; Averianov et al. 2006),
thescelosaurids (including ‘jeholosaurids’, with exception of
Orodromeus), such as Changchunsaurus parvus Zan et al. 2005,
Jeholosaurus shangyuanensis Xu et al. 2000, Yueosaurus tiantaiensis
Zheng et al. 2012 (Scheetz 1999; Butler et al. 2011; Han et al. 2012).
This further differs from some elasmarians, such as Mahuidacursor
lipanglef Cruzado-Caballero et al. 2019 and Macrogryphosaurus
gondwanicus (see Rozadilla et al. 2019), even though this feature
is also absent in other elasmarians, such as Trinisaura santamar-
taensis and Notohypsilophodon comodoriensis (Coria et al. 2013;
Ibiricu et al. 2014).
The absence of a median ventral keel is also observed in the
unnamed ornithopod from the Bajo de la Carpa Formation (MAU-
Pv-LE-617; Jiménez Gomis et al. 2018), non-hadrosauriform dryo-
morphans (e.g. Tenontosaurus tilletti Ostrom 1970), dryosaurids,
and ankylopollexians, such as Camptosaurus dispar (Marsh 1879),
Cumnoria prestwichii (Hulke 1880), Hippodraco scutodens,
Iguanacolossus fortis, and Dakotadon lakotaensis Weishampel and
Björk 1989 (e.g. Gilmore 1909; Galton 1981; Forster 1990;
McDonald et al. 2010). Rhabdodontomorphs, such as Zalmoxes
robustus (Nopcsa 1900) and Mochlodon suessi (Bunzel 1871) (see
Godefroit et al. 2009; Ősi et al. 2012), exhibit a reduction of the
ventral keel, showcasing an evolutionary tendency to diminish in
non-hadrosauriform iguanodontians. Hadrosauriformes demon-
strate, conversely, a secondary development of a ventral keel, as
evidenced in Iguanodon bernissartensis, Mantellisaurus atherfiel-
densis, Morelladon beltrani Gasulla et al. 2015, Ouranosaurus niger-
iensis Taquet 1972, and various hadrosaurids (e.g. Hooley 1925;
Gasca et al. 2015; Verdú et al. 2015). In this regard, NHM-PV
R.3425 shares more similarities with non-hadrosauriform
dryomorphans.
Notably, NHM-PV R.3425 shares with the middle dorsal centra
of some basal ankylopollexians asymmetrical ventral margins in the
lateral view, with a shallower anteroventral heel compared to the
deeper posteroventral one. This configuration is observed in the
middle dorsal centra of the non-hadrosauriform ankylopollexians
Cumnoria prestwichii (Maidment et al. 2022), Camptosaurus dispar
(Gilmore 1909), Uteodon aphanoecetes (Carpenter and Wilson
2008), and Hippodraco scutodens (McDonald et al. 2010). This
trait is also present in Sektensaurus sanjuanboscoi, initially inter-
preted as an indeterminate ornithopod (either elasmarian or igua-
nodontian; see Ibiricu et al. 2019) and recognised here as a non-
hadrosauriform styracosternan (see further below).
Additionally, this feature is absent in thyreophorans (e.g.
Norman et al. 2004b; Raven et al. 2020; Breeden et al. 2021),
elasmarians (e.g. Novas et al. 2019; Cruzado-Caballero et al. 2019;
Rozadilla et al. 2019, 2020), the indeterminate ornithopod MAU-Pv
-LE-617 (Jiménez Gomis et al. 2018), dryosaurids (Galton 1981;
Barrett 2016), Tenontosaurus tilleti Ostrom 1970, rhabdodontids
(Godefroit et al. 2009; Ősi et al. 2012), Hypsilophodon foxii (Hulke
1882), and more advanced styracosternans, such as Iguanacolossus
fortis, Lanzhousaurus magnidens You et al. 2005, Barilium dawsoni
(Lydekker 1888; Norman 2011), Hypselospinus fittoni (Lydekker
1889; Norman 2010), Morelladon beltrani, Iguanodon bernissartenis
(Norman 1980), Mantellisaurus atherfieldensis Hooley 1925
(Norman 1986), Ouranosaurus nigeriensis (Bertozzo et al. 2017),
Equijubus normani You et al. 2003, and Probactrosaurus gobiensis
(Rozhdestvensky 1966). Hence, NHM-PV R.3425 exhibits simila-
rities with some basal ankylopollexians like Camptosaurus dispar,
Cumnoria prestwichii, Uteodon aphanoecetes, Hippodraco scuto-
dens, and Sektensaurus sanjuanboscoi (Gilmore 1909; Carpenter
and Wilson 2008; McDonald et al. 2010; Ibiricu et al. 2019;
Maidment et al. 2022).
NHM-PV R.3425 further differs from the dorsal centra of most
ornithischians given that it bears taller than wide, ellipsoid articular
outlines. In this respect, it differs from the wider than taller, or as
wide as high, articular surfaces found in the dorsal centra of thyr-
eophorans (e.g. Norman et al. 2004b; Raven et al. 2020; Breeden
et al. 2021), marginocephalians (e.g. Butler and Zhao 2009),
10 KAMILA L.N. BANDEIRA ET AL.

rhabdodontomorphs (Godefroit et al. 2009; Ősi et al. 2012),
Tenontosaurus tilleti (Forster 1990), and dryosaurids (Galton
1981; Barrett 2016). The same is true for some elasmarians, such
as Talenkauen santacrucensis (see Rozadilla et al. 2019),
Mahuidacursor lipanglef (see Cruzado-Caballero et al. 2019), and
Macrogryphosaurus gondwanicus (see Rozadilla et al. 2020), even
though other elasmarians show similarly higher than wide dorsal
centra, such as Isasicursor santacrucensis (which still differs from
NHM-PV R.3425 in exhibiting a ventral groove; see Novas et al.
2019). Like Isasicursor santacrucensis, the dorsal centrum of the
indeterminate ornithopod MAU-Pv-LE-617 also resembles NHM-
PV R.3425 in being higher than wide, and distinct in bearing
a ventral groove (Jiménez Gomis et al. 2018). This morphology
also differs from what is seen in the basal ankylopollexians
Camptosaurus dispar Marsh 1879 and Uteodon aphanoecetes
(Carpenter and Wilson 2008) but matches with an array of some
non-hadrosauroid ankylopollexians middle dorsal centra. This fea-
ture is absent in hadrosauriforms, such as Ouranosaurus nigeriensis
(see Bertozzo et al. 2017) and Eolambia caroljonesa Kirkland 1998
(McDonald et al. 2012). NHM-PV R.3425 further resembles
Hippodraco scutodens in the flushed dorsal edge of the posterior
articular surface relative to the anterior articular surface.
In summary, NHM-PV R.3425 resembles the middle dorsal
vertebrae of non-hadrosauriform ankylopollexians due to the
following combination of characters: centrum being subequal
in length and height; higher than wide, ellipsoid articular out-
lines; concave ventral margin in lateral view, with the posterior
ventral projection deeper than the posterior one; and ventral
surface lacking a pronounced keel or ridge. Based on this
combination of features, we regard that NHM-PV R.3425
most closely resembles Cumnoria prestwichii, Hippodraco scuto-
dens, and Sektensaurus sanjuanboscoi. In particular, NHM-PV
R.3425 is most similar to the styracosternan Hippodraco scuto-
dens due to the articular surfaces not being parallel in lateral
view.
Specimen B
Referred material
NHM-PV R.2459, a nearly preserved middle to posterior dorsal
centrum (Figure 7; Table S2).
Locality and horizon
The specimen NHM-PV R.2459 was recovered from sandy shale
facies at the Forte Montserrat (Locality 2), which is located close to
the beaches of Pedra Furada Bay, Salvador City, Bahia State. The
rock layers in this locality are associated with the Ilhas Group, based
on the faciological characterisation provided by Allport (1860), and
correspond to the level of the Valanginian – Hauterivian Marfim
Formation.
Description and comparisons
NHM-PV R.2459 is an isolated dorsal centrum and, as in several
bones studied here, presents a certain degree of weathering. The
centrum is taller than wider, being taller than NHM-PV R.3425,
and has an opisthoplatyan intercentral articulation. The centrum
exhibits well-defined longitudinal striations circumscribing the
articular surfaces (Figure 7A, B), as well as presents numerous
lateral neurovascular foramina as in NHM-PV R.3425. The anterior
articular surface has a subcircular to oval outline (Figure 7E). In
addition, the anterior articular face, as preserved, is slightly trans-
versely wider than the posterior one (Figure 7F), defining a wedge-
shape in lateral and ventral views (Figure 7D) – a common feature
among ornithopods (e.g. Norman et al. 2004a). The ventral margin
is strongly concave in lateral view, showing an offset between the
anterior and posterior faces, with the anteroventral heel projecting
further ventrally than the posteroventral one, as in NHM-PV
R.3425. The lateral and ventral surfaces of the centrum bear several
small neurovascular foramina. The absence of a neural arch hinders
refined comparisons regarding the position of this element along
the dorsal series.
The specimen NHM-PV R.2459 has already been referred as
a dorsal centrum of the tetanuran Megalosaurus by Owen (in
Allport 1860) and after attributed as a probable material of the
pholidosaurid Sarcosuchus hartti by Buffetaut and Taquet (1977).
However, NHM-PV R.2459 differs substantially from theropods
due to the lack of external and internal pneumatic traits, such as
pneumatopores, as usual in presacral elements for Theropoda (e.g.
Benson et al. 2012). This specimen also differs from pholidosaurids,
as well as several other crocodyliforms, given their taller centra,
opisthoplatyan intercentral articulations, and the lack of hypapo-
physis (Souza 2019).
As with NHM-PV R.3425 (see above), this specimen notably
resembles the morphology of non-hadrosauriform ankylopollex-
ians, such as Cumnoria prestwichii, Hippodraco scutodens, and
Sektensaurus sanjuanboscoi, due to the lack of either a ventral keel
or groove, strong concave ventral margin in lateral view (with the
anterior ventral projection deeper than the anterior one; ellipsoid to
suboval articular surfaces, and the centrum being subequal in
length and height. Like NHM-PV R.3425 and Hippodraco scuto-
dens, NHM-PV R.2459 also exhibits articular surfaces that are not
parallel in lateral view.
Specimen C
Referred material
NHM-PV R.3426, represented by a fragmentary middle caudal
centrum; NHM-PV R.3428(a) and NHM-PV R.3428(b), composed
of two posterior caudal centra, which might belong to the same
individual. (Figures 8–9; Table S2).
Locality and horizon
The three elements were recovered at the Mapelle Quarry
(Locality 8). In this locality outcrops flagstones and conglomeratic
sandstones of the Salvador Formation (Massacará Group), which is
partially synchronous with the Ilhas Group, ranging from the
Berriasian to Barremian time-interval.
Description and comparisons
NHM-PV R.3426 is an isolated partial opisthoplatyan centrum
with unpreserved neural arch (Figure 8A–D). The centrum is
approximately rectangular, with only a faint middle constric-
tion, but does not produce an accentuated wedge shape
(Figure 8A,B). The ventral margin, although damaged, seems
HISTORICAL BIOLOGY 11

almost flat (Figure 8E). It is identified here as a middle caudal
centrum due to its moderate elongation, only slightly longer
than tall, as seen in non-hadrosauriform styracosternan mid-
dle-to-posterior caudal centra (e.g. Norman 1980; McDonald
et al. 2012). It is interesting to note that the anterior articular
surface is quadrangular, like the single known anterior caudal
centrum of the holotype of Iguanacolossus fortis (see
McDonald et al. 2010). Such configuration cannot be found
in the other well-known iguanodontian caudal elements, such
as those of Valdosaurus canaliculatus Galton 1975 (Barrett
2016), Tenontosaurus tilletti (Forster 1990), Cumnoria prestwi-
chii (Maidment et al. 2022), Hypselospinus fittoni (Norman
2011), and Ouranosaurus nigeriensis (Bertozzo et al. 2017).
This can also not be found in other known elasmarian caudal
centra (Novas et al. 2019; Rozadilla et al. 2020), nor in other
indeterminate South American ornithopods (Rubilar-Rogers
et al. 2013; Cruzado-Caballero 2017).
The elements NHM-PV R.3428(a) and R.3428(b) are anteropos-
teriorly elongated and slightly dorsoventrally taller than transver-
sally wide. The element ‘a’ (Figure 9A–F) is better preserved than
the element ‘b’ (Figure 9G–L), which is very abraded, and both are
apneumatic. In lateral view, the ventral margins of the centra are
slightly concave (Figure 9A, B, G, H). Ventrally, the element ‘a’ also
present a shallow longitudinal groove (Figure 9D). The intercentral
articulation varies from a slightly platycoelous (Figure 9E,F) to
amphyplatyan (Figure 9K,L).
The specimen NHM-PV R.3426 exhibit a general quadrangular
centrum shape, differing from the middle to posterior caudal centra
of most ornithopods which, although the high of varying shapes,
usually exhibit articular surfaces approximately subequal in width
and height, as seen in elasmarians (e.g. Coria and Salgado 1996a;
Novas et al. 2019; Rozadilla et al. 2019), rhabdodontomorphs (e.g.
Weishampel et al. 2003; Ősi et al. 2012), Tenontosaurus (e.g. Forster
1990), dryosaurids (e.g. Barrett 2016), and iguanodontians such as
Cumnoria prestwichii (Maidment et al. 2022), Camptosaurus dispar,
Uteodon aphanoecetes (Carpenter and Wilson 2008), and
Sektensaurus sanjuanboscoi (Ibiricu et al. 2014). By exhibiting taller
than wide and quadrangular to subcircular articular surfaces, the
Salvador Formation caudal centra are similar to some styracoster-
nans such as Iguanacolossus fortis (McDonald et al. 2010),
Iguanodon bernissartensis (Norman 1980), Mantellisaurus atherfiel-
densis (Norman 1986), Ouranosaurus nigeriensis (at least the mid-
dle elements; Bertozzo et al. 2017), and the El Castellar iguanodont
(García-Cobeña et al. 2023). In this respect, it also resembles the
indeterminate ornithopod from Bajo de la Carpa Formation
(Cruzado-Caballero 2017).
However, the Salvador Formation distal caudal centra lack
the hexagonal shape seen in the articular surfaces found in
many ankylopollexians, such as Cumnoria prestwichii,
Hypselospinus fittoni, Iguanodon bernissartensis,
Mantellisaurus atherfieldensis, and Ouranosaurus nigeriensis.
It also differs from the middle and distal caudal centra of
elasmarians, such as Gasparinisaura cincosaltensis,
Talenkauen santacrucensis, and Isasicursor santacrucensis, in
which the articular surfaces are circular and wider than higher
(Coria and Salgado, 1996a; Rozadilla et al. 2019; Novas et al.
2019). Instead, the articular surfaces of the distal caudal centra
of the Salvador Formation form are closer to the higher than
wide centra with subcircular shape seen in the basal styracos-
ternan Iguanacolossus fortis, the El Castellar iguanodontian
(García-Cobeña et al. 2023), and the Bajo de la Carpa
Formation ornithopod (Cruzado-Caballero 2017).
Figure 7. NHM-PV R.2459, isolated middle to posterior dorsal centrum with iguanodontian affinities (Specimen B) from the Valanginian–Hauterivian Marfim Formation
(Ilhas Group) at Forte Monte Serrat (Locality 2). A, right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views. Anatomical abbreviations: avh, anteroventral
heel; ct, cotyle; nvf, neurovascular foramina; na, neural arch; nc, neural canal; ncj, neurocentral joint; pas, posterior articulation surface; st, striae. Scale bar = 100 mm.
12 KAMILA L.N. BANDEIRA ET AL.

Summarising, the middle caudal NHM-PV R.3426 differs
from most ornithopods, except for Iguanacolossus fortis, in
exhibiting a quadrangular articular surface (McDonald et al.
2010). The distal centra in NHM-PV R.3428 exhibits
a combination of higher than wide articular surfaces, an
opisthoplatyan condition, mild concave ventral margin in lateral
view, presence of a lateral horizontal ridge, and presence of
a slightly ventral groove. This synapomorphic combination of
characters matches with the morphology seen in the posterior
caudal centra of other styracosternans, such as Iguanacolossus
fortis and the El Castellar iguanodontian, and resembles the
Bajo de la Carpa Formation ornithopod as well (Cruzado-
Caballero and Powell 2017). This is consistent with the presence
of non-hadrosauriform styracosternans in the Recôncavo Basin
assemblage as already indicated by the dorsal centra NHM-PV
R.3425 and NHM-PV R.2459.
Specimen D
Referred material
NHM-PV R.3429, a middle caudal vertebra (Figure 10; Table S2).
Locality and horizons
The NHM-PV R.3429 specimen was found at the beach near
Plataforma Station (Locality 3). The shale facies outcropping in
this locality are associated with the Valanginian – Hauterivian
Marfim Formation (Ilhas Group, Recôncavo Basin).
Description and comparisons
NHM-PV R.3429 is an incomplete vertebra, comprised by
most of the centrum and part of the pedicel of the neural
arch (Figure 10A–C). It is interpreted as a caudal due to the
lack of a transverse process, and as a middle caudal due to
its moderate elongation (about as wide as tall) and the lack
of articular facets for chevrons. The intercentral articulation
is platycoelous with subcircular, higher than wide articular
surfaces (Figure 10E,F). The vertebra is apneumatic, and the
neural arch covers entire the dorsal extension of the centrum
(Figure 10C). The ventral surface is smooth, lacking keels or
grooves (Figure 10D). In these respects, this element closely
resembles for the middle caudal vertebrae of several ankylo-
pollexians, such as Cumnoria prestwichii, Hypselospinus fit-
toni, Iguanodon bernissartensis, and Ouranosaurus
nigeriensis. It differs from early-diverging iguanodontians,
such as rhabdodontomorphs (Ősi et al. 2012) and dryosaur-
ids (e.g. Galton 1981), which tend to exhibit mid caudal
articular surfaces about as wide as high. It also differs from
theropods and sauropods for being taller than wide, while in
those saurischians the reverse is more common (Weishampel
et al. 2003).
NHM-PV R.3429 differs from crocodylomorphs, such as
notosuchians and other mesoeucrocodylians, due to the ventral
offset presented and the absence of hypapophyses (e.g. Leardi
et al. 2015). It is notorious that, in general pattern, this speci-
men closely matches with the other Marfim Formation iguano-
dontian material (NHM-PV R.2459 and R.3425), except for the
lack of an asymmetrical ventral margin of the centrum in lateral
view (Figure 10A,B). Given the morphology of this specimen is
consistent with ankylopollexians and closely matches the gen-
eral morphology, we regard that these specimens possibly repre-
sent the same taxon.
Figure 8. NHM-PV R.3426, middle caudal centrum with iguanodontian affinities
(Specimen C) from the Berriasian–Barremian Salvador Formation (Massacará Group)
at Mapelle Quarry (Locality 9). A, right lateral; B, left lateral; C, anterior; D, posterior;
E, ventral views. Anatomical abbreviations: avh, anteroventral heel; ct, cotyle; pas,
posterior articulation surface; pvh, posteroventral heel. Scale bar = 100 mm.
HISTORICAL BIOLOGY 13

Figure 9. NHM-PV R.3428(a) and NHM-PV R.3428(b), associated middle to posterior caudal centra with iguanodontian affinities (specimen C) from the Berriasian–Barremian
Salvador Formation (Massacará Group) at Mapelle Quarry (Locality 9). A-G, right lateral; B-H, left lateral; C-I, dorsal; D-J, ventral; E-K, anterior; F-L, posterior views. Anatomical
abbreviations: aas, anterior articulation surface; ct, cotyle; na, neural arch; nc, neural canal; ncj, neurocentral joint; pas, posterior articulation surface; vg, ventral groove.
Scale bar = 100 mm.
Figure 10. NHM-PV R.3429, isolated middle caudal vertebra with iguanodontian affinities (Specimen D) from the Valanginian–Hauterivian Marfim Formation (Ilhas Group) at
Plataforma Station (Locality 3). A, right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views. Anatomical abbreviations: alf, anterolateral fossa; avh,
anteroventral heel; ct, cotyle; ns, neural spine; pas, posterior articulation surface; prz, prezygapophysis. Scale bar = 100 mm.
14 KAMILA L.N. BANDEIRA ET AL.

Saurischia Seeley 1888
Sauropoda Marsh 1878
Neosauropoda Bonaparte 1986
Diplodocoidea Marsh 1884
Diplodocidae Marsh 1884
Gen. et sp. indet.
Specimen A
Referred material
NHM-PV R.2981(b), a posterior end of a distal middle or proximal
posterior caudal centrum, with a minor portion of the neural arch
(Figure 11; Table S2).
Locality and horizon
NHM-PV R.2981(b) comes from beach outcrops between
Plataforma Station and Itacaranha (Locality 4), Pedra Furada Bay,
and was recovered in the fossiliferous shale intercalated with sand-
stone lenses associated, here associated with the Valanginian –
Hauterivian Marfim Formation.
Description and comparisons
NHM-PV R.2981(b) is represented by an incomplete centrum
lacking most of its anterior portion. However, based on the poster-
ior surface suggests that it might be platycoelous (Figure 11A,B).
Part of the periosteum suffered some abrasion produced by sedi-
mentary particles against the bone and possibly due to some degree
of reworking of the carcass before the final burial (e.g. Shipman
1981). The specimen NHM-PV R.2981(b) exhibits strongly concave
lateral surfaces (Figure 11A,D), as in the rebbachisaurids
Amanzosaurus maranhensis Carvalho et al. 2003, Limaysaurus tes-
sonei Calvo and Salgado 1995, and Itapeuasaurus cajapioensis
Lindoso et al. 2019. In the anterior view, the centrum is strongly
compressed medially and forms an 8-shaped outline, most by the
development of deep blind fossae (Figure 11E). Nonetheless, any
sign of internal pneumaticity on bone tissue is observable. In addi-
tion, there is no signal of an anteroposteriorly oriented ridge in
NHM-PV R.2981(b), differing from the observed in UNPSJB-PV
1004/3, Dicraeosaurus hansemanni Janensch 1914 and Suuwassea
emiliae Harris and Dodson 2004 (Harris 2006; Ibiricu et al. 2012).
In the dorsal view (Figure 11C), a shallow but relatively broad
posterodorsal concavity is present, which is not seen in other
diplodocoids (e.g. Tschopp et al. 2015). Ventrally, NHM-PV
R.2981(b) bears a markedly well-developed hollow that extends
longitudinally (Figure 11D), as in NHM-PV R.3427 (see below),
UNPSJB-PV 1004/3, and Tornieria africana Fraas 1908 (Remes
2006).
In the posterior view (Figure 11F), the centrum is dorsoventrally
elongated like other diplodocids (see Table 2), such as Apatosaurus
ajax Marsh 1877, Brontosaurus parvus Peterson and Gilmore 1902,
and Galeamopus hayi (Holland 1924), but less than middle to
posterior caudal vertebrae of the rebbachisaurid Demandasaurus
darwini Fernández-Baldor et al. 2011. This condition contrasts with
the dorsoventrally compressed caudal centra of Amazonsaurus
maranhensis and other rebbachisaurids, which are more similar to
those observed in flagellicaudatans. The posterior articular face in
NHM-PV R.2981(b) exhibits a roughly circular outline with flat
ventral margin (Figure 11F), like Barosaurus lentus Marsh 1890 and
Suuwassea emiliae, differing from the trapezoidal outlines seen in
Amazonsaurus maranhensis, the unnamed rebbachisaurids from
Cajual island (UFMA 1.10.015, UFMA 1.10.168, UFMA 1.10.188,
and UFMA 1.10.806; see Medeiros and Schultz 2004), and
Figure 11. NHM-PV R.2981(b), fragment of a distal middle or proximal posterior caudal centrum with diplodocid affinities (Specimen A) from the Valanginian–Hauterivian
Marfim Formation (Ilhas Group) at beach between Plataforma and Itacaranha (Locality 4). A, right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views.
Anatomical abbreviations: bf, blind fossa; na, neural arch; pdc, posterodorsal concavity; pas, posterior articulation surface; pdc, posterodorsal concavity; vh, ventral hollow.
Scale bar = 100 mm.
HISTORICAL BIOLOGY 15

Limaysaurus tessonei Calvo and Salgado 1995 (Salgado et al. 2004).
In addition, NHM-PV R.2981(b) displays prominent dorsolateral
expansions, but less developed than in the titanosaurian
Mnyamawamtuka moyowamkia Gorscak et al. 2019.
Specimen B
Referred material
NHM-PV R.3427, represented by a posterior caudal centrum
(Figure 12; Table S2).
Locality and horizon
NHM-PV R.3427 was found at the Mapelle Quarry (Locality 9). In
this locality outcrops flagstones and conglomerate sandstones of the
Salvador Formation (Massacará Group), that ranges from the
Berriasian to Barremian time-interval.
Description and comparisons
NHM-PV R.3427 is a moderately preserved posterior caudal cen-
trum, showing a platycoelous type intercentral articulation and
strongly dorsoventral compression and elongation (Figure 12A,
B), such as the posterior caudal vertebra of Diplodocus carnegii
Hatcher 1901 and Barosaurus lentus (Table 2). A minor part of an
anteriorly displaced neural arch is also observable (Figure 12B),
and both anterior and posterior articulations have an ellipsoid
outline (Figure 12E,F), like Barosaurus lentus and Tornieria
africana.
The lateral surfaces of the centrum are flat. In addition,
restricted blind fossae are present, which are asymmetrically
developed (Figure 12A,B). Dorsally, the neural canal appears
wide, occupying almost entirely the dorsal surface of the cen-
trum (Figure 12C). As in NHM-PV R.2981(b), the dorsal sur-
face also exhibits a broad posterodorsal concavity. However, the
concavity in NHM-PV R.3427 is relatively shallower than in the
NHM-PV R.2981(b), due to its more posterior position in the
caudal series than in the latter specimen. In the ventral view
(Figure 12D), two well-marked ventrolateral ridges are present
and extend until the distal end of the centrum. The ventrolat-
eral ridges in NHM-PV R.3427 are sharper than the present in
NHM-PV R.2981(b) (Figure 11D) and increase in width
towards the lateral edges of the centrum, being more pro-
nounced anteriorly. The development of these ridges delimits
a deep and elongated longitudinal ventral hollow, as in
Tornieria africana (Remes 2006), being straight in shape
through most of its extension. Lastly, NHM-PV R.3427 differs
from NHM-PV R.2981(b) due to the absence of prominent
dorsolateral expansions in the posterior portion of the centrum.
This absence of dorsolateral expansions is also observed in
Barosaurus lentus, especially in the middle to posterior caudal
vertebrae (e.g. Lull 1919). However, this corresponds to another
feature that could represent a change along the individual
caudal series.
Neosauropoda Bonaparte 1986
Macronaria Wilson and Sereno 1998
Titanosauriformes Salgado et al. 1997
Somphospondyli Wilson and Sereno 1998
Titanosauria Bonaparte and Coria 1993
Lithostrotia Upchurch et al. 2004
Gen. et sp. indet.
Referred material
NHM-PV R.2129(a), represented by a complete anterior to mid-
caudal centrum (Figure 13; Table S2).
Locality and horizon
The specimen NHM-PV R.2129(a) was found at the beach outcrops
near Itacaranha (Locality 5), associated with other vertebrate ele-
ments. These specimens come from the gravelly shale facies on
yellowish mudstones that could pertain to the Hauterivian –
Barremian Pojuca Formation.
Description and comparisons
NHM-PV R.2129(a) is a well-preserved and relatively small verteb-
ral centrum, entirely lacking the neural arch. Based on NHM
collection labels, NHM-PV R.2129(a) has been referred to the
dyrosaurid Hyposaurus, given the procoelous nature of neosuchian
vertebrae (e.g. Romer 1956). However, most Hyposaurinae taxa
display platycoelous to amphyplatyan centra (e.g. Schwarz-Wings
et al. 2009), contrasting with strong procoelous morphology seen in
Table 2. Caudal centrum ratios (width-to-height, length-to-height) for selected
sauropod taxa (Modified from Tschopp et al. 2015: table S39).
Taxon mCd-pCd dCd
Shunosaurus lii 1.10 -
Spinophorosaurus nigerensis 0.80 -
Cetiosauriscus stewarti 0.90 -
Losillasaurus giganteus 1.10 -
Camarasaurus lewisi 1.00 -
Giraffatitan brancai 1.20 -
Isisaurus colberti 1.00 -
Haplocanthosaurus priscus 0.90 -
Limaysaurus tessonei - 4.20
Zapalasaurus bonapartei 0.80 -
Nigersaurus taqueti - 3.80
Demandasaurus darwini 1.20 -
Dicraeosaurus hansemanni 1.00 3.60
Suuwassea emilieae 1.00 3.90
Apatosaurus ajax 0.90 -
Apatosaurus louisae 1.00 4.50
Brontosaurus parvus 0.90 -
Tornieria africana 1.10 -
Supersaurus vivianae 1.10 -
Galeamopus hayi <1 -
Diplodocus longus 1.00 -
Diplodocus carnegii 1.35 -
Diplodocus hallorum 1.00 -
Barosaurus lentus 1.30 <5
Salvador Formation diplodocid 1.32 2.68
Marfim Formation diplodocid 0.91 -
A dash indicates the measures which cannot be taken. Abbreviations: dCd, distal
caudal vertebra; mCd, middle caudal vertebra; pCd, posterior caudal vertebra.
16 KAMILA L.N. BANDEIRA ET AL.

NHM-PV R.2129(a). The neural arch restricted on the anterior
portion of the centrum (Figure 13A–C) denotes an unambiguous
titanosauriform synapomorphy (e.g. Salgado et al. 1997; Wilson
2002; D’Emic 2012; Mannion et al. 2013). In contrast, the neural
arch in neosuchians occupies entirely the dorsal surface of the
centrum (e.g. Salisbury and Frey 2001).
The presence of a well-marked serrated neurocentral and
costovertebral joints (Figure 12C), and the diminutive size of
the material as well (ca. 10 cm in length), leads us to believe
that the specimen represents an immature individual (Griffin
et al. 2021). The presence of marked scars of the
M. caudofemoralis or M. ischiocaudalis on both dorsolateral
edges of the centrum (Figure 13A–C) suggest that NHM-PV
R.2129(a) might be a distal anterior or a proximal middle
caudal element (C10?), especially when compare with more
complete caudal series known (e.g. Kellner et al. 2005;
Lacovara et al. 2014). Additionally, the anterior margin of
the neurocentral suture is undifferentiated from the dorsal
edge of the cotyle, strongly linked to the advanced titanosaur
clade Aeolosaurini (Franco-Rosas et al. 2004; Santucci and
Arruda-Campos 2011; Bandeira et al. 2019).
The centrum has a developed procoelous type of intercen-
tral articulation, in which the condyle apex is flushed above
the longitudinal axis of the centrum, as in advanced titano-
saurians (Powell 2003; Poropat et al. 2021). This condition
differs from that observed in mamenchisaurids, turiasaurians,
dicraeosaurids, and diplodocids, in which the procoely is
limited to the anteriormost elements and its convexity apex
is there below the longitudinal axis of the centrum (Mannion
et al. 2019). The presence of procoelous middle caudal
Figure 12. NHM-PV R.3427, isolated posterior caudal centrum with diplodocid affinities (Specimen B) from the Berriasian–Barremian Salvador Formation (Massacará Group)
at Mapelle Quarry (Locality 9). A, right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views. Anatomical abbreviations: aas, anterior articular surface; bf,
blind fossa; na, neural arch; ncj, neurocentral joint; pdc, posterodorsal concavity; pas, posterior articulation surface; pdc, posterodorsal concavity; rm, rock matrix; vlr,
ventrolateral ridge; vh, ventral hollow. Scale bar = 50 mm.
Figure 13. NHM-PV R.2129(a), isolated middle caudal centrum with lithostrotian affinities from the Hauterivian–Barremian Pojuca Formation at Itacaranha (Locality 5). A,
right lateral; B, left lateral; C, dorsal; D, ventral; E, anterior; F, posterior views. Anatomical abbreviations: cd, condyle; ce, condylar edge; cf, chevron facet; ct, cotyle; cvj,
costovertebral joint; lco, lateral concavity; nc, neural canal; ncj, neurocentral joint; vh, ventral hollow; vlr, ventrolateral ridge. Scale bar = 100 mm.
HISTORICAL BIOLOGY 17

vertebrae is observed on several Upper Cretaceous titanosaur
taxa, such as Baurutitan britoi and Dreadnoughtus schrani. In
contrast, titanosaurs from the Lower Cretaceous exhibit
a wide array of intercentral articulation types, varying from
platycoelous, amphyplatyan, and mildly procoelous middle
caudal vertebrae, as in Malawisaurus dixeyi Haughton 1928
(Gomani 2005) and Mnyamawamtuka moyowamkia (Gorscak
et al. 2019). NHM-PV R.2129(a) exhibits strongly procoelous
middle caudal centra as in the contemporaneous
(Valanginian – Hauterivian) taxa Tengrisaurus starkovi
Averianov and Skutschas 2017 (see also Averianov et al.
2021, 2023), Volgatitan simbirskiensis Averianov and Efimov
2018, as well as ‘Iuticosaurus valdensis’ (NHM-PV R. 146 and
R.151) and the unnamed titanosaur NHM-PV R.5333 from
Wessex Formation (Le Loeuff 1993; Upchurch et al. 2011).
In the anterior view (Figure 12E), the cotyle has
a subcircular outline that slightly tapers ventrally. The ventral
margin in this region is almost straight, a common feature of
anterior to middle caudal vertebrae due to the attachment
area decreasing for the M. caudofemoralis longus along the
tail (Salgado and García, 2002). Laterally, the centrum of
NHM-PV R.2129(a) is markedly concave, as in
Maxakalisaurus topai Kellner et al. 2006 and aeolosaurines.
The cotyle margin is slightly inclined anteriorly, but not as
strongly as in Aeolosaurus rionegrinus Powell 1987,
Gondwanatitan faustoi Kellner and Azevedo 1999, and
Uberabatitan ribeiroi Salgado and Carvalho 2008 (Bandeira
et al. 2019; Silva et al. 2019). The ventral face of the centrum
bears prominent ventrolateral ridges (Figure 12D), likewise
many titanosaurian taxa, such as Andesaurus delgadoi Calvo
and Bonaparte 1991, Hamititan xinjiangensis Wang et al.
2021, and Saltasaurus loricatus Bonaparte and Powell 1980
(Powell 1992). These ridges border a shallow longitudinal
hollow, as in the holotypic caudal vertebra of ‘Titanosaurus
indicus’ (GSI-2191.2194; Mohabey et al. 2013), Isisaurus col-
berti Jain and Bandyopadhyay 1997 (Wilson and Upchurch
2003) and saltasaurines. However, NHM-PV R.2129(a) differs
from the latter due this fossa is not well excavated, as in
Saltasaurus loricatus and Rocasaurus muniozi Salgado and
Azpilicueta 2000 (Sanz et al. 1999; Powell 2003; Zurriaguz
and Cerda 2017). Similarly, to GSI-2191.2194, the NHM-PV
R.2129(a) specimen has two chevron facets, present on both
anterior and posterior portions of the centrum, but less
developed than in the Indian taxon (see Wilson and
Upchurch 2003: Figure 4A). In addition, NHM-PV
R.2129(a) lacks a marked mediolaterally compression, which
gives a houglass-like shape to the centrum, as present in GSI-
2191.2194. The articular surfaces for chevrons in the anterior
face of NHM-PV R.2129(a) are oriented anteroventrally,
while on the posterior one, the facets are ventrally oriented.
Although not preserved in this specimen, this pattern indi-
cates that chevrons of the NHM-PV R.2129(a) specimen had
double articular facets, as in aeolosaurines (Santucci and
Arruda-Campos 2011). Posteriorly, the developed condyle is
featureless, lacking characteristic notches or sulcus
(Figure 12F).
Saurischia Seeley 1888
Theropoda Marsh 1881
Averostra Paul 2002
Gen. et sp. indet.
Referred material
NHM-PV R.2982, a right pedal phalanx IV-1 (Figure 14; Table S3).
Locality and horizon
The specimen have been found in the beach outcrops between
Plataforma Station and Itacaranha (Locality 4), Pedra Furada Bay,
and recovered from fossiliferous shale intercalated with sandstone
lenses. These facies are associated with the Valanginian –
Hauterivian Marfim Formation.
Description and comparisons
The pedal phalanx NHM-PV R.2982 is relatively well preserved
and presents some erosion on its surface, along the articular face
of the proximal region. The specimen is dorsoventrally com-
pressed in its midpoint (Figure 14A–D), acquiring
a subtriangular shape on the distal portion (Figure 14F). It is
elongated, robust, and rectangular in both dorsal and ventral
views (Figure 14A,C). The phalanx is asymmetrical, maintaining
a misalignment of its margins (Figure 14B,D). The distal articu-
lation is ginglymoid (Figure 14A,E), while the proximal one is
rounded and has a deep and wide collateral ligament pit. Robust
and dorsoventrally compressed pedal phalanx are remarkable
among abelisauroids and basal tetanurans (Coria et al. 2002;
Novas et al. 2004; Carrano 2007; Brusatte et al. 2009; White
et al. 2013). It contrasts with the slender, dorsoventrally taller,
and elongated phalanx of noasaurids, some basal coelurosaurians,
ornithomimosaurians, and maniraptorans (Novas 1997;
Choiniere et al. 2010, 2012, 2014; Egli et al. 2016; Langer et al.
2019). Laterally, NHM-PV R.2982 has two heels proximally:
a proximomedial (Figure 14A), which is more expanded and
rounded distally; and a proximolateral (Figure 14C) that is
slightly taller and triangular. In lateral view, the specimen has
a rectangular outline rather than a sharp triangular one
(Figure 14B,D), as observed in Majungasaurus crenatissimus
(Depéret 1896), Sinraptor dongi Currie and Zhao 1994,
Allosaurus fragilis (Marsh 1877), and the carcharodontosaurid
SHN.039 (Malafaia et al. 2019).
The flexor tubercle, in the lateral view, is aligned with the
bottom of the proximal articulation. The dorsal surface of the
distal articulation is marked by a shallow extensor groove, as in
most theropods (Figure 14A). On the medial surface, an ellip-
soid collateral pit marks the proximal portion, close to the
articulation and above the posteroventral heel. The lateral col-
lateral pit is slightly wider than the medial one. The ventral
surface is almost flat and has a rectangular aspect with a small
concavity in the proximal direction. Medially, the wider collat-
eral pit and tall and laterally inclined ginglymus indicate that
the NHM-PV R.2982 is a right pedal phalanx. The concave
proximal articulation lacking a medial keel, the deepness of
the extensor groove and the presence of a posteroventral heel
indicates that the specimen is a phalanx IV-1 (e.g. Currie and
Zhao 1993; Carrano 2007; Malafaia et al. 2019). The lack of
comparative specimens with completely preserved pedes, as well
18 KAMILA L.N. BANDEIRA ET AL.

as diagnostic features among postcranial skeleton of several
theropod lineages, only allows an assignment to a large-bodied
averostran theropod. NHM-PV R.2982 was recovered with other
theropod remains (see below), suggesting that the specimen
may belong to the same individual of NHM-PV R. 2980 or
NHM-PV R.2981(a).
Averostra Paul 2002
Tetanurae Gauthier 1986
Orionides Carrano et al. 2012
Megalosauroidea Fitzinger 1843
a. Spinosauridae Stromer 1915
Gen. et sp. indet.
Referred material
NHM-PV R.2980, one complete and well-preserved anterior caudal
centrum (Figure 15; Table S2). The theropod phalanx NHM-PV
R.2982 was recovered from the same locality. However, the lack of
additional data regarding the collection of the specimens hampers
a secure association between both specimens as pertaining to the
same individual.
Locality and horizon
The specimen was found in Locality 4, the beach outcrops between
Plataforma Station and Itacaranha, Pedra Furada Bay, recovered
from fossiliferous shale intercalated with sandstone lenses. These
facies are associated with the Valanginian – Hauterivian Marfim
Formation.
Description and comparisons
The vertebral centrum NHM-PV R.2980 is rectangular in both
lateral, dorsal, and ventral views (Figure 15A–D), being subequal
in elongation and height. The intercentral articulation is amphicoe-
lous (Figure 15E,F), as in megalosauroids and abelisaurids, such as
Pycnonemosaurus nevesi Kellner and Campos 2002 (Benson 2010;
Mateus et al. 2011; Delcourt 2017; Malafaia et al. 2017, 2020). This
feature contrasts with other ceratosaurians and avetheropods, in
which the caudal centrum is constricted towards the midline, con-
ferring a spool-like shape (e.g. Bonaparte 1991; Brochu 2003;
Benson 2008; Persons and Currie 2011). NHM-PV R.2980 presents
the posterior articulation dorsoventrally taller than the anterior
articulation area (Figure 15E,F). NHM-PV R.2980 has a greater
ventral extension in the lateral view (Figure 15A,B), presenting
a lateral offset. It also differs from the unnamed spinosaurid from
the Araripe Basin (MN 4743-V; Bittencourt and Kellner 2004) and
Ichthyovenator laosensis Allain et al. 2012, which presents a parallel
dorsoventral extension of articular areas.