Two new catfish species of typically Amazonian lineages in the Upper Rio Paraguay (Aspredinidae: Hoplomyzontinae and Trichomycteridae: Vandelliinae), with a biogeographic discussion

Abstract

Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one of the genus Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae, Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper Paraguay system. Paracanthopoma saci is distinguished from its only congener, P. parva, by a spatulate caudal peduncle; a minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater Amazonian river systems (Amazon, Orinoco, Essequibo and smaller surrounding drainages). Their presence restricted to the Rio Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed using S-DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the Paraguay and Amazon drainages.

Full text

Two new catfish species of typically
Amazonian lineages in the UpperRioParaguay
(Aspredinidae: Hoplomyzontinae
and Trichomycteridae: Vandelliinae),
withabiogeographic discussion
Fernando Cesar Paiva Dagosta¹ & Mário de Pinna²
¹ Universidade Federal da Grande Dourados (UFGD), Faculdade de Ciências Biológicas e Ambientais (FCBA). Dourados, MS, Brasil.
ORCID: http://orcid.org/0000-0001-7163-296X. E-mail: ferdagosta@gmail.com (corresponding author)
² Universidade de São Paulo (USP), Museu de Zoologia (MZUSP). São Paulo, SP, Brasil.
ORCID: http://orcid.org/0000-0003-1711-4816. E-mail: pinna@ib.usp.br
Abstract. Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one
of the genus Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae,
Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper
Paraguay system. Paracanthopoma saci is distinguished from its only congener, P.parva, by a spatulate caudal peduncle; a
minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two
separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the
origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed
among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the
presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly
larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater
Amazonian river systems (Amazon, Orinoco, Essequibo and smaller surrounding drainages). Their presence restricted to the Rio
Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed
using S-DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay
from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their
presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is
also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the
Paraguay and Amazon drainages.
Keywords. Systematics; Ichthyology; Biogeography; Taxonomy; Candiru; Siluriformes; Paracanthopoma; Ernstichthys.
INTRODUCTION
Historical biogeography, like most historical
sciences, is a discipline that studies the past and
therefore is not optimized for formulating predic-
tions about the future (Morrone, 2009). On the
other hand, historical biogeography is efficient in
making retrodictions, i.e., to “predict” past events
(Morrone, 1997, 2009). Of course, its predictions
apply to not-yet-known results of past events.
With progress in knowledge about phylogenet-
ic relationships and distribution of Neotropical
fishes, it becomes increasingly clear how geomor-
phological past events shaped ichthyological di-
versity (Albert & Reis, 2011; Dagosta & de Pinna,
2018; Albert etal., 2020). Because fishes have ex-
tremely limited dispersal abilities across land, the
ichthyofaunal composition of a basin is an imprint
of its history with other basins. However, such
historical portrait is both complex and imperfect.
Complex due to its temporally mixed context and
imperfect because biological events such as dis-
persal, hybridization and extinctions tend to be
blurred with time. Temporal mixing results from
overlapping geomorphological processes that
cause hydrological mixing between neighboring
basins (i.e., connection, diversion, sector capture,
etc.). Consequently, basins present a mosaic of
fish assemblages composed of elements from
different geographic origins recruited across dif-
ISSN On-Line: 1807-0205
ISSN Printed: 0031-1049
ISNI: 0000-0004-0384-1825
Pap. Avulsos Zool., 2021; v.61: e20216147
http://doi.org/10.11606/1807-0205/2021.61.47
http://www.revistas.usp.br/paz
http://www.scielo.br/paz
Edited by: Carlos José Einicker Lamas
Received: 18/03/2021
Accepted: 12/04/2021
Published: 19/04/2021
ARTICLE
http://zoobank.org/31481179-ADAD-48BF-BD7E-F326BEE7999A

ferent times and events (Lima & Ribeiro, 2011; Dagosta
etal., 2014; Dagosta & de Pinna, 2017).
Herein we discuss the evidence and underlying caus-
es for two new siluriforms which are particularly elo-
quent testimonies of Amazonian affinities of the upper
rio Taquari, rio Paraguay basin. The first one is a para-
sitic catfish of the genus Paracanthopoma, of subfamily
Vandelliinae, family Trichomycteridae. The second one
is an Ernstichthys, of subfamily Hoplomyzontinae, fam-
ily Aspredinidae. Both taxa belong to previously exclu-
sive-Amazonian-core lineages (Paracanthopoma and
Hoplomyzontinae, respectively) and were collected sym-
patrically and syntopically in the Rio Taquari.
The Vandelliinae includes the only exclusively hema-
tophagous gnathostomes besides vampire bats. Their ev-
er-lasting popular fame stems from their occasional and
accidental penetration of natural openings of the human
body (Spotte, 2002). Vandelliines feed exclusively on
blood as adults, a behavior that is general for all species
in the group. Normally they enter the gill cavity of prey
fishes, lacerate a blood vessel, gorge on blood and leave,
but variant strategies are known to exist across the taxo-
nomic diversity of the group, although as yet poorly un-
derstood (Kelley & Atz, 1964; Zuanon & Sazima, 2004). The
Vandelliinae comprises four genera: Paracanthopoma,
Paravandellia, Plectrochilus, and Vandellia (a fifth genus
with four new species is currently under description
by the authors). The subfamily as a whole occurs in the
Amazon, Orinoco, Essequibo, Magdalena, and Parana-
Paraguay, but its center of diversity is by far the Amazon,
where all genera and a majority of species are found.
Actually, as yet only two species of Vandelliinae are
known to occur outside the Amazon-Orinoco-Essequibo
realm, both of Paravandellia: P.oxyptera Miranda-Ribeiro,
1912 from La Plata and Amazon and P. phaneronema
(Miles, 1943) from the Rio Magdalena basin.
Paracanthopoma currently comprises a single de-
scribed species, P. parva Giltay, 1935, but new species
in the process of description will increase that diversity
by an order of magnitude (de Pinna & Dagosta, inprep.).
The genus is easily diagnosable by several unique mor-
phological characteristics, among which the presence
of a free fold of integument across the isthmus, a trait
whose significance is recognized since the original de-
scription of the taxon and which remains valid today.
Species of Paracanthopoma occur throughout lowlands
and uplands of the Amazon, Orinoco, and Essequibo,
but were so far absent outside of those basins. Given
the amount of ichthyological surveying so far conduct-
ed in the Paraná-Paraguay, São Francisco, and Coastal
Brazilian drainages, combined with the conspicuousness
of Paracanthopoma species and their abundance in the
Amazon, it seemed highly unlikely that the genus oc-
curred outside the broad Amazonian realm. Still, small
pockets of hidden diversity exist and herein we report on
a new species of Paracanthopoma which unexpectedly
surfaced in the Rio Taquari, upper Paraguay. It seems to
be a narrowly endemic form, and is the first of its genus
from outside the Amazon-Orinoco realm. This is the first
new species of Vandelliinae described since 1943.
The Hoplomyzontinae is the rarest and least known
aspredinid subfamily. The first described member of the
group was Hoplomyzon atrizona Myers, 1942 and rec-
ognition of a suprageneric taxon came with Fernández-
Yépez (Fernández-Yépez, 1953). Additional diversity has
been slow in forthcoming and collections of hoplomy-
zontines are still rare. However, there is evidence that
their abundance and ecological relevance may be far
larger than current sparse museum collections seem to
suggest (Taphorn & Marrero, 1990). The subfamily con-
tains Dupouyichthys Schultz, 1944 (1 sp.), Ernstichthys
Fernández-Yépez, 1953 (3spp.), Hoplomyzon Myers, 1942
(4spp.), and Micromyzon Friel & Lundberg, 1996 (2spp.)
and all its species are small-sized. The morphology of
hoplomyzontines is aberrant, with several adaptations
unique among siluriforms, including a complex body
armor composed of shield- and plate-like modifications
derived from different skeletal elements. Despite being
such an obvious object of interest for morphological in-
vestigation, the anatomy of Hoplomyzontinae remained
poorly-known until recently, with fragmentary informa-
tion scattered in various publications. This situation be-
gan to change with Carvalho etal. (2016) and Carvalho
etal. (2017) which offered an unprecedented picture of
the osteology of Micromyzon orinoco and Hoplomyzon
cardosoi. Hoplomyzontine taxonomy is relatively tidy,
as might be expected for such a small group, but some
generic limits are based on rather limited character ev-
idence. Phylogenetically, while monophyly of hoplomy-
zontines is unchallenged and extremely well-supported
(Friel, 1994; Cardoso, 2008; Carvalho et al., 2018), their
relationships within Aspredinidae are still controver-
sial. Some studies support the genus Xyliphius as sister
group to Hoplomyzontinae (Friel, 1994) while some oth-
ers place the subfamily as sister group to different sub-
sets of aspredinids (Cardoso, 2008; Carvalho etal., 2018).
Proposals of relationships within hoplomyzontines also
diverge, with some hypotheses placing Hoplomyzon
as sister group to the rest of the subfamily, with
Micromyzon as sister to Dupouyichthys plus Ernstichthys
(Friel & Lundberg, 1996) and others with the positions of
Hoplomyzon and Micromyzon switched relative to that
one (Cardoso, 2008).
Geographically, hoplomyzontines are mostly restrict-
ed to Andean piedmonts in the western Amazon, west-
ern Orinoco, Maracaibo and Magdalena drainages in a
distribution pattern called Cis-Andean Foothills (Dagosta
& de Pinna, 2019). Exceptions to that pattern are the two
lowland Amazonian and Orinocoan species of the ge-
nus Micromyzon (Friel & Lundberg, 1996; Carvalho etal.,
2016) and a few isolated and taxonomically yet poorly
understood records of Ernstichthys and “Dupouyichthys”
in lower portions of Rio Madeira (Ohara & Zuanon, 2013)
and of Ernstichthys in the Rio Pilcomayo in Bolivia and
upper Rio Tocantins (Jarduli etal., 2014; Tiago Carvalho,
pers.comm.). In any case, the geographic distribution of
the Hoplomyzontinae known to date seemed to be solid-
ly restricted to the northern basins of South America. The
discovery of a new hoplomyzontine species in the rio
Taquari was therefore as surprising as the finding of its
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
2/23

co-occurring Paracanthopoma. Given such unusual cir-
cumstances, it is fitting to describe them together in this
publication, as taxonomic supplements to a discussion
on the biogeographical implications of the Amazonian
components of the upper Rio Paraguay.
MATERIAL AND METHODS
Specimens were collected under the collecting per-
mit # 60634/1 issued to F.C.P.D. by the Instituto Chico
Mendes de Conservação da Biodiversidade (ICMBio) of
the Ministry of Environment. Fishes were anesthetized
through Eugenol solution, according to the protocol
of Lucena etal. (2013). Standard length (SL) is given in
millimeters. In morphometric data, subunits of the body
are expressed as percentages of SL and subunits of head
as percentages of head length (HL). Measurements
were point-to-point, taken with digital calipers to the
nearest 0.1 mm, except for subunits of the head in
Paracanthopoma, which were obtained with an ocular
micrometer and therefore as projections. Definitions of
measurements and meristics for Paracanhopoma fol-
low Reis & de Pinna (2019). Odontodes were counted
on cleared and stained (c&s) preparations, and included
odontodes that are attached to bone, or replacement
odontodes in the process of filling in for an already de-
tached odontode, or an obviously empty socket which
happens to have lost both its occupant and replacement
odontode. Claw-like teeth were counted as those actu-
ally attached to the premaxilla, with replacement teeth
and sockets mentioned separately in the description. The
integument fold acros the isthmus in Paracanthopoma,
called a branchiostegal or branchial membrane by pre-
vious authors, is here called a branchiostegal velum,
to reflect its particular structure unique to the genus
(see Discussion below). Definitions of measurements
for Ernstichthys follow Carvalho et al. (2015). Vertebral
counts include all preural vertebrae, including five in
the Weberian apparatus for hoplomyzontines, but not
for Paracanthopoma, plus the terminal complex PU1+U1
counted as one. The differentiated U2 of Ernstichthys (as
in other Aspredinidae) was not included in counts (de
Pinna & Ng, 2004). In the description, the frequency of
each count is provided in parentheses after the respec-
tive count, with the count of the holotype indicated by
an asterisk. Cleared and counterstained specimens for
comparative material were prepared according to Taylor
& Van Dyke (1985). High-resolution CT scan figures are
available at the online repository Harvard Dataverse
https://dataverse.harvard.edu/dataverse/harvard, avail-
able at http://doi.org/10.7910/DVN/XCXEM8 (Dagosta,
2021). Radiographs were taken with a Faxitron digi-
tal x-ray model. Number of serrations on the posteri-
or margin of the pectoral spine from other species of
Ernstichthys were taken from the literature (e.g., Ohara &
Zuanon, 2013; Stewart, 1985) and from material exam-
ined at MZUSP. Osteological observations in the new
Ernstichthys were done by computerized tomography of
the holotype only. Osteological terminology follows de
Pinna (1996), with the lacrimal being shorthand for the
compound lacrimal+antorbital (de Pinna etal., 2020). So
called “bony plates” in hoplomyzontines are anatomically
heterogeneous. The lateral series is formed from expand-
ed lateral-line ossicles, and are thus independent dermal
bones. Remaining plate-like structures in the dorsal and
ventral series are part of internal skeletal structures that
emerge at the surface, thus not really independent der-
mal plates. The term plates is thus herein reserved for el-
ements of the lateral series, while the dorsal and ventral
series are called shields. Plates independent of both inter-
nal structures and lateral-line canals, such as in some lo-
ricarioids (Callichthyidae, Scoloplacidae, Loricariidae) are
absent in hoplomyzontines. Lists of types and compar-
ative material include catalog numbers followed by the
number of specimens in alcohol, their SL range, number
of c&s specimens and respective SL range. Institutional
abbreviations follow Sabaj (2020).
Biogeographic analyses
Ancestral geographic distributions were recon-
structed using statistical dispersal-vicariance analysis
S-DIVA (Yu etal., 2010) and BBM (Ali etal., 2012) in RASP
(Yu etal., 2015). Those models are the only ones avail-
able for ancestral reconstruction from trees without
branch lengths in RASP. Trees were built in Mesquite
(Maddison & Maddison, 2019) and exported in Nexus
format to RASP. In the case of Trichomycteridae, the
MTSVG clade from Ochoa etal. (2017) was supplemented
Table1. Distribution of taxa coded in S-DIVA. Biogeographical regions: A=
Amazon-core; B= São Francisco and Eastern Coastal drainages; C= Paraná-
Paraguay; D= Trans-Andean.
Trichomycteridae Aspredinidae
Listrura
B
Pseudobunocephalus
AC
Microcambeva
B
Acanthobunocephalus
A
Potamoglanis
AC
Hoplomyzon
AD
Stauroglanis
A
Micromyzon
A
Sarcoglanis
A
Ernstichthys
AC
Typhlobelus
A
Bunocephalus chamaizelus
A
Pygidianops
A
Aspredinichthys
A
Tridens
A
Aspredo
A
Tridensimilis
A
Platystacus
A
Tridentopsis
AC
Xyliphius
ACD
Stegophilus
AB
Pterobunocephalus
AC
Haemomaster
A
Amaralia
AC
Ochmacanthus
AC
Bunocephalus
ABCD
Homodiaetus
B
Amaralia
AC
Megalocentor
A
Dupouyichthys
D
Henonemus
A
Pareiodon
A
Acanthopoma
A
Pseudostegophilus
AC
Paracanthopoma saci
C
Paracanthopoma parva
A
Paravandellia oxyptera
AC
Paravandellia phaneronema
D
Vandellia
A
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
3/23

with the addition of two valid species of Paravandellia.
Morphological evidence supports the genus as the sister
group to Paracanthopoma (DoNascimiento, 2015), and
its inclusion in the analysis is biogeographically relevant.
For Aspredinidae, the tree used was from Carvalho etal.
(2018), with the addition of Dupouyichthys, sister genus
to Ernstichthys (Friel, 1994; Friel & Lundberg, 1996) and
therefore important for a biogeographic understanding
of the group. Coding of terminal distributions was at the
genus level (Table1), except in case of Paravandellia and
Paracanthopoma where relationships at species level
were necessary for biogeographic accuracy. Analyses in
S-DIVA and BBM were conducted with default settings
(comparative analyses conducted with more aggres-
sive parameters yielded the same general results). Four
biogeographical regions were defined: A = Amazon-
core; B= São Francisco and Eastern Coastal drainages;
C= Paraná-Paraguay; D= Trans-Andean. The number of
maximum ancestral areas was set to the maximum, lim-
ited by the number of regions previously determined (4
areas each in Trichomycteridae and Aspredinidae).
RESULTS
Paracanthopoma saci sp.nov.
http://zoobank.org/6536E8CD-A751-4CEF-AD74-FAA3669F99D6
(Figs.1‑2)
Holotype: MZUSP 125624, 19.1 mm SL, Brazil, Mato
Grosso do Sul, Alcinópolis, Rio Taquarizinho (tributary
to Rio Taquari, Rio Paraguay drainage) (18°12′14.8″S,
53°34′11.3″W), elev. 363m, col. F. Dagosta, A. Ferreira, R.
Zanon, 18Sep2019.
Paratypes: MZUSP 125626, 13 ex (2 c&s),
14.5-21.8 mm SL, collected with holotype. MZUSP
125622, 2 ex, 19.5-19.9 mmSL, same locality and col-
lectors as holotype, 17Sep 2019. MZUSP 115585, 1 ex,
19.3 mm SL, Brazil, Mato Grosso do Sul, Alcinópolis,
stream tributary to Rio Taquari (Rio Paraguay drain-
age) at dirt road between Alcinópolis and road MS-217
(18°12′16.5″S, 53°34′13.5″W), col. O.T. Oyakawa, P.
Camelier, M. Marinho, F. Dagosta, 26 Aug 2013. MNRJ
53559, 2ex, 14.6 -16,8mmSL, from MZUSP 125626.
Diagnosis
Distinguished from the only other species of
Paracanthopoma, P.parva, by: 1)short and anteriorly-dis-
placed opercular patch of odontodes, which leaves a
large posterior free area of integument continuous with
the rest of the head integument around it (as a conse-
quence of that morphology, in dorsal view the posterior
tips of the opercular odontodes do not reach the base
of the pectoral fin); 2)pelvic fin with three rays (vs. five);
3)opercle lacking an ascending process (vs. ascending
process present); 4) caudal peduncle spatulate by hy-
pertrophied series of 22-29 (upper) and 20-29 (lower)
procurrent caudal-fin rays (vs. caudal peduncle narrow,
with 15 to 19 upper and 14 to 18 lower rays); 5)median
premaxillary dentition feeble, with three delicate teeth
(vs. median premaxillary dentition robust, with nine
large strong teeth); 6) supraorbital canals opening as
two separate s6 pores (vs. canals fused at midline and
opening as single median s6 pore); 7)caudal fin slightly
convex or truncate, with round edges (Fig.2; in Fig.1 the
apparent emarginated margin is a preservation artifact)
(vs. bilobed or emarginate, concave); 8) supraoccipital
lacking anterior median process (vs. supraoccipital with
produced anterior process); 9)origins of dorsal and anal
fins approximately at same vertical (vs. origin of dorsal
fin clearly anterior to vertical through origin of anal fin).
The three former characters also distinguish P.saci from
all undescribed species of the genus known to the au-
thors at this time.
Figure1. Paracanthopoma saci, MZUSP 125624, holotype, 19.1mmSL. Brazil, Mato Grosso do Sul, Alcinópolis, Rio Taquarizinho. (a)Lateral view, (b)Dorsal view of
head, (c)Ventral view of head. Photos by V. Reis.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
4/23

Description
Morphometric data provided in Table2. Body elon-
gate. Cross-section of body as broad as deep at pecto-
ral-fin insertion and increasingly compressed posterior to
that point, tapering to caudal fin. Dorsal profile of body
in broad gentle arc, nearly straight, from head to origin of
dorsal fin (Figs.1-2). Dorsal midline with transparent fin
fold anterior to dorsal fin. Dorsal and ventral profiles of
caudal peduncle straight immediately posterior to ends
of dorsal and anal fins, then expanded by dorsal and
ventral procurrent caudal-fin rays resulting in symmetri-
cally spatulate caudal peduncle. Ventral profile of body
nearly straight until pelvic-fin origin, but greatly distend-
ed in some specimens due to gut contents. Myotomes
and longitudinal skeletogenous septum clearly visible
through thin integument along whole body. Axillary
gland large, elongate, positioned dorsal to pectoral-fin
base and extending posteriorly approximately to mid-
length of adpressed pectoral fin, its large round or oval
pore located at its posterior terminus. Some specimens
preserved with large amount coagulated secretion still
attached to pore.
Dorsal profile of head continuous with that of dorsum.
Head longer than broad, snout very broad, semicircular
with a continuous round anterior margin. Head muscles
not entering skull roof. Head depressed (head depth ap-
proximately 50% of head width) with dorsal profile most-
ly continuous from nape to tip of snout. Ventral profile of
head straight, flattened, though externally irregular due
to integument folds. Eye size slightly less than one-third
of snout length, without free orbital rim, located dorsal-
ly on head and directed dorsolaterally. Integument over
eyes thin and transparent. Center of eyes located slightly
anterior to middle of HL, interorbital width equal to, or
slightly larger than, longitudinal diameter of eye. Eye lens
unconstricted by iris, entirely exposed on external aspect
of eye. Anterior nostril small, surrounded by short tu-
bule of integument produced posteriorly into small and
pointed flap. Anterior internarial width slightly narrower
than interorbital. Posterior nares slightly larger than an-
terior ones, oval (longer than broad) in shape, located
close to anteromesial margin of eyes. Center of posterior
nares slightly anterior to transverse line through anterior
margin of eyes. Posterior internarial width slender than
interorbital and approximately twice as wide as antero-
posterior length of nostril.
Opercular patch of odontodes tiny, dorsolaterally
located on head, on dorsal half of head depth in later-
al view, anterodorsally to pectoral-fin base. Opercular
odontodes six, disposed in two irregular rows. Odontodes
with distal portions curved medially. Opercular fold of
integument vestigial or absent, instead continuous with
large well-delimited roundish area of thickened integu-
ment resembling a vastly hypertrophied opercular fold.
Interopercular patch of odontodes miniscule, nearly
invisible on surface of head, located ventrolaterally on
head, horizontally aligned with origin of pectoral fin.
Interopercular odontodes four. Interopercular patch
of odontodes closer to opercular patch than to eye.
Interopercular flap of integument absent or vestigial.
Mouth ventral and small, strongly flattened ven-
trally, delineated anteriorly and laterally by vast cres-
cent-shaped upper lip and posteriorly by small lower lip.
Each premaxilla with a single claw-like tooth attached to
its distal tip, and one additional tooth socket with part-
ly-formed tooth in parallel. Claw-like tooth deeply hidden
in labial tissue and difficult to expose in preserved speci-
mens without damaging soft tissue. Conical teeth absent
on premaxilla. Upper lip very broad but poorly-differen-
tiated, continuous with ventral surface of snout. Median
Figure2. Live coloration of Paracanthopoma saci. Lateral view of MZUSP 125622, 19.9mmSL.
Table2. Morphometric data of Paracanthopoma saci. Ranges, mean and SD
(standard deviation) include holotype. Head subunits were obtained with an
ocular micrometer and therefore as projections.
n holotype min max mean SD
Standard length (mm)
8
19.1
15.4
21.1
18.1
1.8
Total length
8 112.5 17.3 23.5 20.3 2.0
Body depth
8 13.1 11.7 15.7 13.9 1.5
Caudal-peduncle length
8
25.1
24.0
26.6
25.0
1.0
Caudal-peduncle depth
8 9.9 8.9 11.3 9.8 0.8
Predorsal length
8
68.6
66.5
69.2
68.2
0.9
Preanal length
8 67.5 65.5 68.8 67.2 1.1
Prepelvic length
8 60.2 56.0 61.1 59.4 1.5
Dorsal-fin base length
8
9.4
6.8
10.3
8.6
1.2
Anal-fin base length
8 11 7.6 11.0 9.0 1.0
Pectoral-fin length
8
11.5
9.7
12.3
10.8
0.8
Head length (mm)
8 15.7 15.1 16.1 15.7 0.4
Head width
8 83.6 83.6 100.0 89.2 5.1
Head depth
8
41.8
41.8
54.6
50.3
4.0
Interorbital
8 13.6 12.6 15.5 13.8 1.0
Eye diameter
8
12.7
11.3
13.6
12.8
0.7
Snout length
8 36.4 35.8 39.8 37.2 1.4
Mouth width
8 23.6 14.6 28.6 24.6 4.3
Anterior internarial width
8
15.5
14.6
21.8
17.2
2.4
Posterior internarial width
8 10.9 9.7 13.6 11.0 1.2
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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premaxilla miniscule, with three closely-set tiny teeth.
Dermal pad of median premaxilla semicircular. Lower
jaw narrow, its anterior profile M-shaped and composed
mostly of produced dentary lobes, continuous with men-
tal region posteriorly. Jaw cleft short, strongly directed
posteriorly, but curved laterally at posterior end. Dentary
diastema as deep median concavity between dentary
lobes. Dentary teeth four on each side, large but difficult
to visualize in alcoholic specimens, concentrated at me-
sial end of dentary and directed anteromesially, arranged
in two ventral and two dorsal ones, not aligned. Dentary
teeth long, their axis anteriorly-directed at base, but
curved dorsally or dorsolaterally at distal half. Median
tooth of ventral row longer than others.
Branchiostegal membrane continuous posteriorly
with large, continuous, posteriorly concave, free bran-
chiostegal velum across whole of ishtmus region. Dorsal
portion of branchiostegal velum reaching and slight-
ly overlapping anterior margin of pectoral-fin base.
Branchial opening small, located anteriorly to pecto-
ral-fin base, approximately equal to space between oper-
cular and interopercular patches of odontodes. Maxillary
barbel ranging from extremely short to vestigial, extend-
ing maximally for one-third distance between its base
and base of interopercular patch of odontodes. Posterior
point of its base slightly anterior to vertical through an-
terior margin of eye in lateral view. Rictal barbel vestigial,
reduced to small knob mesially to base of maxillary one,
absent in some specimens. Nasal barbel vestigially rep-
resented by posterior elongated portion of fold around
anterior naris described above.
Lateral line short, approximately half of pectoral-fin
length, and straight, extending alongside dorsal margin
of anterior portion of axillary gland. Terminal lateral-line
pore immediately dorsal to axillary gland opening. Short
secondary branch splitting off ventrally from proximal
portion of main canal, with corresponding pore opening
anteriorly to midlength of main canal. Single lateral-line
tubule poorly calcified, extending over part of main ca-
nal immediately posterior to bifurcation.
Pectoral fin small, approximately 60% of HL, with
i+4 rays in all specimens (except i+3 in one side of one
specimen). Pectoral-fin morphology with pronounced
variation, with most specimens (n = 9, including ho-
lotype) having triangular pointed shape with first ray
slightly longer than others. Some specimens (n = 5)
with all rays equally long, resulting in truncate fin mar-
gin. Two exceptional specimens in MZUSP 125626 (14.5
and 15.0mmSL) with hypertrophied first pectoral-fin ray
forming long filament. First ray corresponding to 36%SL
in smaller specimen and 26% SL in larger specimen,
with filamentous portion approximately 2 and 1.5 times
length of rest of fin, respectively (see Remarks below).
Pelvic fins minute, closely set together at base, with i+2
rays (with all three rays unbranched in small specimens;
one specimen with vestigial additional ray posteriorly).
Pelvic splint present in single of three c&s specimens.
Origin of pelvic fin close to origin of anal fin, well ante-
rior to vertical through origin of dorsal fin, extending
posteriorly well beyond anus and urogenital papilla and
slightly beyond origin of anal fin. Posterior margin of pel-
vic fin gently convex. Dorsal fin elongate, roughly trian-
gular with roundish edge and gently convex, sinusoidal
or straight distal margin. Dorsal-fin rays v-viii*+I*-II+5-6*.
Anal fin similar in shape to dorsal fin, with v-ix(viii*)+I+5
rays. Origin of anal fin at or slightly posterior to vertical
through origin of dorsal-fin. Caudal fin roughly rectangu-
lar in preserved position.. Margin of caudal fin truncate
with round edges and gently convex margin (in Fig.1 the
apparent emarginated margin is an artifact of the preser-
vation position of middle rays). Principal caudal-fin rays
5+5* or 4+5. Procurrent caudal-fin rays 22-29 dorsally
and 20-29 ventrally.
Vertebrae (exclusive of Weberian complex) 40 (n=2),
41 (n=3), 42* (n=4), 43 (n=3). First dorsal-fin pterygio-
phore positioned subsequent to neural spine of vertebra
22 (n=3). First anal-fin pterygiophore positioned subse-
quent to hemal spine of vertebra 22 (n=1) or 23 (n=2).
Dorsal- and anal-fin pterygiophores six, poorly calcified
or entirely cartilaginous, clearly visible only in c&s prepa-
rations. Branchiostegal rays three. Ribs one pair.
Pigmentation in alcohol
General aspect of fish almost entirely white. Post-
orbital part of skull roof with extensive dark field formed
by brain pigment seen by transparency, its anterior mar-
gin strongly concave, in continuous arc or angulate, im-
mediately posterior to eyes. Well-defined elongate dark
field extending anterior to eye, along lateral margin of
olfactory capsule. In some specimens, mesial margin
of olfactory capsule also with some dark pigment, but
much weaker than lateral one. Dark pigment on body
restricted to uniform web-like or dotted covering on dor-
sal part of abdominal wall and few isolated small spots
along base of dorsal fin and, rarely, of anal and caudal
fins and muscular margins of caudal peduncle. Posterior
portion of vertebral column with internal dark pigment
on each individual vertebra, forming series of spots vis-
ible externally by transparency along caudal peduncle
(more evident in life). All fins hyaline.
Pigmentation in life
Based on Fig.2. General body color translucent yel-
lowish. Neural canal darkly pigmented along entire ver-
tebral column, forming continuous thin dark line along
whole body. Hemal canal forming reddish line ventrally
along vertebral column. Limits between vertebrae from
middle of abdomen to base of caudal skeleton outlined
in dark by internal pigment. Branchial region pink and
cardiac region intense red due to blood seen by trans-
parency. Abdomen yellow anteriorly and abruptly dark
posteriorly due to ingested blood. Dorsal portion of ab-
domen with iridescent golden speckles, concentrated on
its anterior and posterior limits. Eggs and fatty globules
faintly visible along dorsal part of abdomen. Superficial
integumentary dark pigmentation as described in pre-
served specimens.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
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Figure3. Distribution map of Ernstichthysspp. (open dots) and Paracanthopomaspp. (black diamonds). Red star indicates type-locality of Ernstichthys taquari and
Paracanthopoma saci.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
7/23

Ecology
The Rio Taquarizinho is ca. 15 m wide at the col-
lection locality. Water is clear, slightly milky and with
moderate current. Specimens were collected by sein-
ing on sand banks in the middle of the river, especially
in sectors shaded by riparian vegetation. There was no
aquatic vegetation and depth of collection ranged from
30 to 150 cm. Paracanthopoma saci is sympatric with
Paravandellia oxyptera (MZUSP 125623, 125625) with
both relatively abundant at the type locality. The two spe-
cies are psammophilic, but with different microhabitat
preferences. Paracanthopoma saci favors fine sand, while
P.oxytera prefers sectors with coarser granulation. Once
the subtleties of their preferences are understood, it is
possible to target one or the other species for collection
with reasonable accuracy. Segregation is not complete
however, and occasionally they were captured together
in the same net (F. Dagosta, pers.obs.). The abdomen is
distended with blood in several specimens. Some female
specimens (two each in MZUSP 125622 and 125626)
have large eggs, approximately eye-sized or slightly larg-
er, visible by transparency (Fig.2). Distribution of eggs
extending along ventral margin of hypaxial musculature
from shortly posterior to end of pectoral fin to nearly end
of abdominal cavity, with approximately 20 eggs visible
in lateral layer of each side (certainly more in inner por-
tions of gonad).
Etymology
The name honors the SACI expedition (South
American Characiform Inventory, under direction of
N. Menezes) which collected the first known specimen
of this species. Appropriately, Saci is also the name of
a Brazilian rural folklore supernatural entity (complete
name: saci-pererê), personified as a nocturnal, one-
legged, hopping, red-capped, pipe-smoking black boy,
transmutable into dust devils and fond of mischievous
deeds aimed at terrorizing or annoying people and other
animals.
Remarks
Paracanthopoma saci is the only species of
Paracanthopoma outside of the core Amazonian drain-
ages (see Geographical Distribution above) and only the
second species of Vandelliinae from the entire Paraná-
Paraguay basin (the other being Paravandellia oxyptera).
In addition to the new species of Ernstichthys reported
below, other fish collected with P. saci were all typical
members of the Paraná-Paraguay fish fauna, including
some endemics (e.g., Cyphocharax gillii, Steindachnerina
brevipinna, Creagrutus meridionalis, Brachychalcinus ret-
rospina). As a member of Paracanthopoma, P. saci is a
genus-level addition to the general composition of the
Paraguay basin.
Two paratypes of Paracanthopoma saci have ex-
traordinarily elongated first pectoral-fin rays (part of
MZUSP 125626, see Description above). This is the most
extreme case of filamentous pectoral-fin ray known in
Trichomycteridae (where the filament is never longer
than the length of the rest of the fin). No other speci-
mens of the species show any sign of fin elongation. The
significance of this trait is difficult to interpret with the in-
formation available. The two filamentous specimens are
identical in all other relevant characteristics to other pu-
tative conspecifics, there being thus no reason to suspect
that they might represent a different taxon. At 14.5 and
15.0mmSL, those two specimens are among the small-
est known of P.saci. Sexual dimorphism in pectoral-fin
size and structure exists in all species of Paravandellia
and some undescribed species of Paracanthopoma, with
mature males having a stouter and larger pectoral fin, a
differential particularly pronounced in the first ray (MdP,
pers.obs.). No such association is evident in P.saci. An al-
ternative hypothesis of juvenile specialization is possible.
The longest filament, corresponding to 36%SL, is seen
in the smallest specimen. In the second specimen, only
slightly larger, the filament is reduced to 26%SL. Other
specimens similar in size to the latter show no sign of fil-
ament. So, if the filament is indeed a juvenile specializa-
tion, it is reduced very abruptly in the course of ontogeny
(or perhaps broken off). Resolution of this question will
have to await additional material and data.
The extremely reduced opercular and interopercular
armatures of Paracanthopoma saci, a reduction reflected
in their vestigial (opercular) or absent (interopercular) in-
tegument folds, raises questions about the functionality
of that complex in the species. One specimen in MZUSP
125626 is preserved with opercular odontodes erect, a
sign that the biomechanical links usually associated with
the movement of the opercular patch of odontodes are
still functional in the species. No such evidence exists for
the still more reduced interopercular armature. Given
that the latter is not only tiny in size in P. saci but also
quite buried in integument, it may be reduced to a ves-
tigial condition. Reductions of opercular and interoper-
cular armature are recurrent in different lineages of
sand-dwelling trichomycterids, such as psammophilic
taxa in Glanapteryginae and Sarcoglanidinae. Despite
such reductions, it is certain that P.saci is hematopha-
gous like all other vandelliines, because several speci-
mens in MZUSP 125626 have visible coagulated blood in
their guts.
Geographic distribution
The species is so far known from a single locality in
the Upper Rio Taquari system (Rio Paraguay drainage). It
marks the southernmost limit of the genus.
Conservation status
Paracanthopoma saci is endemic to Brazil and only
known from its type-locality at the upper Rio Taquari.
Its area of occupancy (AOO) (B2) 4km² is based on this
only known record. The AOO is likely underestimated
and since its hematophagous habits may mean that its
transported by host fish over distances beyond its own
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
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(vs. i+7); by the presence of i+6 anal-fin rays (vs. viii+4);
by the basipterygium entirely hidden in integument (vs.
anterolateral arm of basipterygium exposed on the skin,
forming rugose shield).
Description
General body aspect, shape and pigmentation in
Figs.4-5. Morphometric data in Table3. Dorsal and ven-
tral profiles of body and head in nearly mirror images of
each other, gently convex to origins of dorsal and anal
fins, respectively, then straight along to nearly end of
caudal peduncle. Greatest depth of body at posterior
part of head and greatest width between bases of pec-
toral-fin spines. Caudal peduncle depressed for most of
its length, except for compressed terminus near base
of caudal fin. Caudal peduncle least deep at ca. three-
fourths of its length. Head depressed, gently convex in
dorsal and ventral profiles. Mid-dorsal cephalic region
with three bony prominences disposed in line, anterior
one occipital, at limit between supraoccipital and neu-
ral complex of Weberian apparatus, second one formed
by posterior part of neural complex of Weberian appa-
ratus and third one immediately anterior to dorsal fin,
formed by central portion of middle nuchal plate (Fig.6).
Anterior cranial fontanel large, elongate-ovoid, with an-
terior portion narrower than posterior one, occupying
most of body of mesethmoid and anterior half of length
of frontals. Posterior fontanel about 30% shorter and 10%
narrower (at widest portion) than anterior one (Fig.6A),
delimited mostly by frontals and only posterior end by
supraoccipital. Frontals mostly separated from each oth-
er at midline by fontanels, contacting at a small portion
at their midlength, corresponding to the epiphyseal bar,
Table3. Morphometric data of Ernstichthys taquari. Range, mean, and SD
(standard deviation) include holotype.
holotype n min max mean SD
Standard length (mm)
20.2
3
20.2
22.8
21.9
1.5
Depth at dorsal-fin origin
24.8 3 23.3 24.8 23.9 0.8
Snout to dorsal-fin origin
30.2
3
28.7
30.2
29.4
0.8
Snout to pectoral-fin origin
16.8 3 16.1 16.8 16.6 0.4
Snout to pelvic-fin origin
36.5 3 35 36.5 35.5 0.8
Snout to anal-fin origin
18.8 3 17.1 18.8 17.8 0.9
Caudal-peduncle depth
8.6 3 7.9 8.6 8.2 0.3
Caudal-peduncle length
20.8
3
18.9
20.8
19.8
1.0
Pectoral-fin length
17.5 3 17.1 17.5 17.3 0.2
Pelvic-fin length
45.3
3
44.6
45.4
45.1
0.4
Pelvic-fin origin to anal-fin origin
14.5 3 14.2 14.8 14.5 0.3
Dorsal-fin length
18.8
3
18.3
19.9
19.0
0.8
Dorsal-fin base length
35.1 3 34.9 35.6 35.2 0.4
Anal-fin length
16.8
3
15.2
16.8
15.8
0.9
Anal-fin base length
56.0 3 55.5 56.2 55.9 0.4
Eye to dorsal-fin origin
6.6 3 6.6 8.4 7.3 1.0
Dorsal-fin origin to caudal-fin base
23.4 3 22.1 23.4 22.6 0.7
Head length
32.6 3 31.3 32.6 31.9 0.7
Horizontal eye diameter
41.3
3
41.3
43.1
41.9
1.1
Snout length
9.1 3 7.6 9.1 8.2 0.8
Interorbital width
18.4
3
18.4
22
20.5
1.9
Upper jaw length
56.9 3 56.9 62 59.4 2.5
vagility limits, as reported for a congener (Zuanon &
Sazima, 2005). Although the Rio Taquari has historically
been reported to carry a large sediment load, this charac-
teristic has intensified starting in the late 1970’s, with the
increase of agriculture and pasture in the region (Soriano
etal., 2001). It has been proposed that Quartzipsamment
soils in the region are important sources of sediments
that intensify siltation of the Taquari (Galdino etal., 2013),
which is considered as the most serious environmental
and socio-economic problem in the Pantanal (Soriano
etal., 2001). Because P.saci is hematophagous, it is nec-
essary to better know its natural hosts. If such hosts are
migratory species, they may also be negatively impacted
by siltation, thus representing a threat to the feeding re-
sources of P.saci. Such a situation represents a continu-
ing decline of habitat quality. At present, none of those
factors are known in any detail and therefore we sug-
gest the species is assessed as DD (iii) according to the
International Union for Conservation of Nature (IUCN)
categories and criteria (IUCN, 2020).
Ernstichthys taquari sp.nov.
http://zoobank.org/17ADE44D-AB3D-407A-AA08-9011EFE0F470
(Figs.4‑6)
Holotype: MZUSP 125825, 22.8 mm SL, Brazil, Mato
Grosso do Sul, Alcinópolis, Rio Taquarizinho (tributary
to rio Taquari, rio Paraguay drainage) (18°12′14.8″S,
53°34′11.3″W), elev. 363m, col. F. Dagosta, A. Ferreira, R.
Zanon, 18Sep2019.
Paratypes: MZUSP 125826, 2ex, 20.2-22.7 mmSL, col-
lected with holotype.
Diagnosis
Ernstichthys taquari differs from all congeners by:
1)the relatively narrow bilateral bony shields on dorsal
and ventral series, which do not overlap or contact each
other anywhere in both series (vs. adjacent shields con-
tacting or overlapping along most or entire series; this
trait also distinguishes the species from most hoplomy-
zontine species except those of Hoplomyzon); 2)the pres-
ence of seven or eight serrations on the posterior margin
of the pectoral spine (vs. 10-18); 3)the pectoral-fin spine
only slightly larger than subsequent soft rays, so that
there is a gradual transition between the spine and the
rest of fin (vs. spine 25% longer or more than soft rays,
leaving large portion of protruding spine without cor-
responding fin web distally). Further distinguished from
E. megistus by the presence of a well-developed rictal
barbel (vs. barbel absent or reduced to bump). Further
distinguished from E.intosus by the unbranched maxil-
lary barbel (vs. with thread-like secondary barbels); by
the lack of dentations along the anterior margin of the
pectoral fin (vs. dentations present); by the presence of
two pairs of stout and regularly-positioned mental bar-
bels (Figs.4-5; vs. over 100 thread-like and uniformly dis-
tributed barbels); by the presence of i+4 dorsal-fin rays
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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Figure4. Ernstichthys taquari, Brazil, Mato Grosso do Sul, Alcinópolis, Rio Taquarizinho State, MZUSP 125825, holotype, 22.8mmSL. (a)Lateral view, (b)dorsal view,
(c)ventral view. Photos by V. Reis.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
10/23

with two frontals forming H-shaped configuration in
dorsal view. Supratemporal fossa (not visible externally)
roughly oval, positioned between posterior portion of
mesial margin of pterotic and posterior portion of later-
al margin of supraoccipital (Fig.6). Transverse process of
vertebra 5 slender, expanded distally and curved slightly
posteriorly (Fig.6A), its distal edge exposed at surface of
integument. Eye small, located dorsally on head slightly
anteriorly to middle of HL, twice as close to midline as to
lateral margin of head in dorsal view (Figs.4-5). Eye visi-
ble only partially in lateral view (Figs.4-5). Axillary gland
pore small, slit-like when collapsed, located immediate-
ly posterodorsally to base of pectoral fin. Vent located
slightly anterior to transversal through midlength of last
pelvic-fin ray. Integument heavily covered with uncul-
liferous papillae on dorsal part of head and dorsal and
lateral sides of body, most prominently over area around
margins of neurocranium, snout, basal half of dorsal sur-
face of maxillary barbels and cheeks. Unculiferous tuber-
cles homogeneously scattered on body, not arranged in
rows or any other regular pattern. Ventral side of head
with papillae softer and larger than those on dorsal side
of head and rest of body.
Anterior nares encircled by short tubule, longer pos-
teriorly, and separated from each other by distance short-
er than interorbital. Posterior nostrils larger than anterior
ones, separated from eye by one orbital diameter and
partly covered by anteromesial flap of skin. Posterior na-
res more widely separated from each other than anteri-
or ones, by distance approximately equal to interorbital.
Mouth subterminal, slightly wider than interorbital, with
both jaws in gentle continuous arcs, and lower jaw short-
er than upper jaw. Teeth entirely absent on both jaws.
Upper lip well delimited laterally by tumescent maxil-
lary barbel bases, with large irregular-shaped and posi-
tioned papillae immediately at mouth opening. Lower
lip smooth at edge of mouth but densely large-papillate
further posteriorly, with papillate covering extending
onto mental region. Mandibles thin and delicate, lack-
ing bony contact at symphysis. Premaxillae shaped as
large elongate plates jointly forming nearly continuous
concave bony shield internally on upper jaw. Each pre-
maxilla with large stout ascending process near midline,
dorsoposteriorly accomodating mesethmoid cornua.
Barbels eight: one pair maxillary, one pair rictal and two
pairs mental. Maxillary barbel large, flat and expand-
ed basally, forming most prominent feature on head.
Maxillary barbel doubly adnate, dorsally from proximal
two-thirds of its posterior margin to cheek and ventrally
from base of rictal barbel to mental region immediately
anterior to anterior mental barbel. Skin folds of adnation
forming deep pocket lateral to rictus and anterior to cor-
onoid process of mandible. Rictal barbel short, directed
ventrally or ventrolaterally, inserted ventrally at anterior
Figure5. Ernstichthys taquari, MZUSP 125826, paratypes. Left side specimen 20.2mmSL: (a)lateral view, (b)dorsal view, (c)ventral view; right side specimen
22.7mmSL: (d)lateral view, (e)dorsal view, (f)ventral view.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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attachment of ventral adnation of maxillary barbel, Two
pairs of mental barbels inserted close to lateral margin
of ventral side of head; posterior one twice as long and
thick as anterior one. Branchiostegal membranes broad-
ly united to isthmus, without free fold. Gill openings ven-
tral, reduced to small oblique slits anteromedial to inser-
tions of pectoral spines, approximately twice as wide as
width of pectoral-fin spine base. Branchiostegal rays four,
first one short and thin, attached to middle of anterior
ceratohyal. Remaining three branchiostegal rays longer
and stouter than first one, attached to posterior end of
anterior ceratohyal.
Pectoral fin large, I+6+i *(3), with soft branched rays
thin and delicate, shorter than spinous ray but not to
same degree as in other species of Ernstichthys. Pectoral-
fin spine long, 35-36% of SL, with triangular soft tissue
cap distally. Anterior margin of spine smooth, without
serrations. Posterior margin with seven large pungent
antrorse serrations, progressively larger distally, plus
one or two proto-spinous bony bumps basally. Cleithral
bullae large and conspicuous, forming widest part of
body and head in dorsal view. Postcleithral process large,
broad and abruptly narrow and pointed distally, reach-
ing to middle of Weberian centrum in lateral view, and al-
most to vertical through tip of coracoid process. Posterior
coracoid process long, slightly curved mesially distally,
its tip reaching half-length of basipterygium and almost
to base of pelvic fin. Pelvic fin long and pointed, insert-
ed well anteriorly to vertical through origin of dorsal fin,
i+5*(3), with first ray thickest of series and 30% shorter
than second. Second pelvic-fin ray longest of series and
thicker than all other rays except first. Basipterygium
with long pointed posterior process reaching almost to
transversal through anterior tips of first ventral shield.
Dorsal-fin origin well anterior to half of SL, entirely ad-
nate posteriorly, to end of last fin ray. Dorsal spinelet (or
first spine, or spine lock) absent, first ray (homologous
to main dorsal-fin spine) not spinous, flexible, segment-
ed and without serrations. Dorsal-fin rays I+4*(3). Four
dorsal-fin pterygiophores broad and angulate in shape,
pierced by large irregular fenestrae. Anterior nuchal plate
absent. Remaining nuchal plates described above under
dorsal shield series (Fig.6). Adipose fin absent. Anal fin
insertion at vertical through end of dorsal-fin base, partly
adnate, to ca.two-thirds of last ray, with small free edge
at end. Anal-fin rays i+6*(3), third and fourth rays longest.
Seven anal-fin pterygiophores progressively smaller pos-
teriorly, four anterior ones squarish and irregularly fenes-
trated, posterior three rectangular and lacking fenestrae.
Caudal fin 5+4*(3), with lower lobe longer than upper
one as consequence of elongate lower principal fin-rays.
Profile of upper lobe straight or gently sinusoidal, that
of lower lobe convex and round. All principal rays close-
ly set, nearly adpressed at base. Outer rays thicker and
with bases much stouter than that of remaining rays.
Procurrent caudal-fin rays represented by single ventral
element, spine-like and bent near base. Dorsal procur-
rent caudal-fin rays absent.
Body armored with three series of bony elements:
dorsal, ventral and lateral, all of which heavily cov-
ered with integument and not conspicuous on surface
of body. Dorsal and ventral series running alongside
mid-dorsal and mid-ventral lines, respectively. Lateral
series extending along midlateral line of each side of
body. Dorsal series formed by 21 heavily ornamented
shields extending from immediately anterior to dor-
sal fin to end of body. Four of those shields disposed
alongside base of dorsal fin. First shield of dorsal series
formed by greatly expanded posterior nuchal plate,
supported by bilateral dorsal processes of vertebra
8. Remaining 20 dorsal shields formed by expanded
tips of bilateral dorsal processes (Fig.6) on vertebrae
9 to compound ural centrum. Anterior fourteen verte-
brae-derived shields bilateral, gradually closer together
at the midline posteriorly. Posterior six shields median,
progressively narrower posteriorly. Elements of dorsal
shield series not overlapping each other and not con-
tacting those of lateral series, except for last one which
barely touches dorsal margins of penultimate and an-
tepenultimate lateral plates. Ventral shield series with
16 heavily ornamented bony shields, with two anterior
ones anterior to anal fin. First shield largest, formed by
distal expansions of hemal arch of vertebra 9, broader
anteriorly than posteriorly and with concave anterior
and posterior margins, its anterior margins produced
into anterolateral processes distally approaching pos-
terior processes of basipterygia. Second ventral bony
shield immediately anterior to anal fin, lozenge-shaped
and formed by distally-expanded first anal-fin ptery-
giophore. Remaining 14 shields formed by distal ex-
pansions of bilateral ventrolateral vertebral processes,
extending to posterior-most vertebra anterior to caudal
centrum. Of those, nine anterior ones bilateral (six of
which disposed alongside anal-fin base) and remain-
ing five ones median, latter clearly formed by conflu-
ence of bilateral portions. Posterior five ventral shields
broader than long, except for long isosceles-triangular
last element. Ventral shields not overlapping each other
and not contacting any element of lateral series. Lateral
series composed of actual plates or scutes, contrary to
dorsal and ventral series, and formed by modified and
hypertrophied lateral-line ossicles lacking direct con-
tact with vertebral column. Lateral shields not orna-
mented and covered with thick integument, not readily
visible on external aspect of body. Transition of lateral
line tubules into plates gradual, starting at ninth ossi-
cle, approximately at vertical though end of dorsal-fin
base, and progressively more expanded towards caudal
fin. Overlap among plates starting at ossicle 15, form-
ing complete shield on sides of body from that point
on. Total of 34 plates, each with central blunt knob of
thickened bone except for last one (Fig.6), collectively
forming lateral serration. Knobs gradually less promi-
nent posteriorly, covered with thick soft skin and con-
centration of papillae. Knobs centrally located on ante-
rior plates but gradually displaced dorsally starting on
24th plate. Spacing between knobs slightly decreasing
towards caudal fin.
Total vertebral count 29 (including those in Weberian
complex). Ribs absent.
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Figure6. High-resolution x-ray computerized microtomography (HRXCT) of Ernstichthys taquari, MZUSP 125825, holotype, 22.8mmSL. (a)Dorsal view, (b)lat-
eral view of left side, (c)ventral view. acf: anterior cranial fontanel; ach: anterior ceratohyal; ang: anguloarticular; bp: basipterygium; br: branchiostegal rays; cl:
cleithrum; co: coracoid; cv: complex vertebra; den: dentary; ds: dorsal shield element; eap: expanded first anal-fin pterygiophore (=second ventral shield); ehs:
expanded hemal spine (=first ventral shield); fr: frontal; hyo: hyomandibula; io1: first infraorbital; iop: interopercle; let: lateral ethmoid; lp: lateral plate element
(=expanded lateral-line ossicle); mes: mesethmoid; mnp: middle nuchal plate; mx: maxilla; op: opercle; pa: parasphenoid; pal: palatine; pch: posterior ceratohyal;
pfr: pelvic-fin rays; pfs: pectoral-fin spine; pmx: premaxilla; pnp: posterior nuchal plate (=first dorsal shield); pso: parietosupraoccipital; pto: pterotic; pv5: para-
pophysis of fifth vertebra; qu: quadrate; sc: posttemporosupracleithrum; spo: sphenotic; vh: ventral hypohyal; vs: ventral shield element.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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Pigmentation in alcohol
Pattern of dark pigmentation highly variable. Four
conspicuous saddles of dark coloration across dorsolat-
eral surface of body, extending in faded version ventrally
and gradually smaller posteriorly. White round areas in
dorsal view between first, second and third dark saddles,
due to concave profiles of posterior margin of first saddle,
anterior and posterior profiles of second one and anterior
profile of third one. First dark saddle largest, covering en-
tire area between pelvic- and dorsal-fin bases, extending
over basal half, or more, of latter. Dorsal area and shape of
saddle variable. In one paratype restricted to doubly-con-
cave band across most of anterior part of dorsal fin, but
not to base of spine (Fig.5E). In other paratype, band
covers broad squarish area on and around anterior half
of dorsal fin, extending anteriorly continuously as narrow
straight mid-dorsal dark band over occipital region and
then expanding laterally as bilateral wings over posterior
margin of neurocranium (Fig.5B). In holotype, anterior
saddle vast, covering entire dorsum and sides in continu-
ous dark area from anterior 60% of dorsal fin to posterior
third of head. Second dark saddle immediately posterior
to end of dorsal fin, extending ventrally and narrowing to
end of anal-fin base, its mid-lateral part prolongued an-
teriorly and in one paratype broadly cojoining anteriorly
with first saddle along midlateral line. Third dark saddle
beginning approximately at posterior third of caudal
peduncle. Fourth saddle smallest, covering region of
proximal portions of caudal-fin rays but not reaching last
ventral ray. Cheeks with dark cloud extending ventral-
ly towards pectoral-fin base and region around base of
posterior mental barbel. In holotype and one paratype,
dark cheek fields continuous dorsally with striking trans-
versal dark band across eyes (trans-ocular band), forming
conspicuous mask-like pattern. Barbels white, except for
uniform dark covering on dorsal surface of proximal half
of maxillary-barbel base in holotype and one paratype
(Fig.5E). Axillary gland pore white. Tubercles on dorsal
and lateral surfaces of body and head lighter than sur-
rounding areas. Individual bony knobs along lateral-line
shield series lighter than rest of adjacent integument, due
to concentration of white tubercles. Central part of abdo-
men almost entirely covered with extensive continuous
dark field from base of pelvic fins to mental region, in one
paratype with long light losenge-shaped area between
bases of posterior mental barbels. Abdominal dark field
continuous posteriorly with darker fields on and between
bases of pelvic fins and anteriorly fading before lower lip.
Area of branchial opening conspicuously lighter than
surrounding region. Vent light or white but finely rimmed
in dark. Bilateral elongate white fields posterolaterally to
vent, converging towards midline posteriorly. Dorsal-fin
solid dark on anterior half or 60%, with distal portion cov-
ered only with scattered cromatophores over fin rays and
hyaline margin. Anal fin mostly white, with faint irregular
dark fields not forming any pattern. Caudal fin with dark
saddle described above over base of fin rays, followed by
narrow white vertical band and then faint irregular dark
smudges over rest of fin web, abruptly fading on its distal
fifth. Pectoral fin with large dark field crossing distal por-
tion of first soft fin ray and mid-distal adjacent portion
of pectoral-fin spine. Small independent dark spot over
bases of last four rays. Rest of pectoral fin with scattered
dark chromatophores. Distal portion of pectoral-fin spine
and soft-tissue terminus abruptly white. Dorsal surface
of pelvic fins covered with irregular dark fields denser
than those on anal fin. Ventrally, very dark field cover-
ing basal portion of rays and region between fin bases,
continuous anteriorly with remainder of abdominal dark
pigmentation.
Ecology
Ernstichthys taquari was collected in a white water riv-
er, with moderate water flow, over substrate composed
of rock and sand. Contrary to most hoplomyzontines, its
habitat is not the deep bottom of a large river, but rather
a small river accessible by hand-seining. Aquatic macro-
phytes were present in some sites and riparian forest was
well preserved. All specimens were collected in a shaded
sector covered with dense vegetation and large rocks on
the bottom. The species was not locally abundant at the
time of collection, with only three specimens found in
the course of five hours of collecting effort.
Etymology
The specific name taquari is a reference to the rio
Taquari. The word is of Tupi language origin (takwa’ri)
combining ta’kwara (a common name for bamboo-like
plants of family Poaceae) plus ‘i’ for diminutive. A noun
in apposition.
Remarks
Intraspecific variation in pigmentation in Hoplomy-
zontinae has been well-documented in Micromyzon
akamai (Chuctaya etal., 2020) and in Hoplomyzon sexpa-
pilostoma (Taphorn & Marrero, 1990). The variation pat-
tern described for H.sexpapilostoma is similar to that in
E.taquari, with some individuals with a dark band across
the eyes (trans-ocular band) and others without it. This
is the same kind of variation here observed in E.taquari
(cf., Fig.5). Taphorn & Marrero (1990) associated the pres-
ence of a differentiated trans-ocular band with females
and juvenile specimens. In males, the band is reported
to expand and to become undifferentiated from the
pigmentation of the rest of head. Another sexually-di-
morphic coloration trait observed by those authors in
H. sexpapilostoma is the size and intensity of the dark
spot on the distal portion of the pectoral fin and spine.
Taphorn & Marrero (1990) note that the marking is larg-
er and darker in males. In E.taquari, a single specimen
lacking the trans-orbital dark band does not noticeably
differ from other specimens in the size of its pectoral fin
spot. Unfortunately, the limited number of specimens
available does not allow at this time the sex verification
of individuals of E.taquari. Thus, the possible association
of such pigmentation variation with sexual dimorphism
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remains unverified in the species. In any case, the parallel
of the two pigmentation patterns of E.taquari with those
in H. sexpapilostoma are highly suggestive of a similar
sexually-dimorphic association.
An unidentified species of Ernstichthys from the Rio
Araguaia was reported and illustrated by Jarduli et al.
(2014) and hypothesized as sister group to clade E.an-
duzei + E.megistus (Cardoso, 2008). The photograph in
Jarduli etal. (2014, p. 507) shows a fish similar to E.taquari
in dorsal and lateral views, but with some visible dif-
ferences. The strongly bent distal portion of the pecto-
ral spine of the Araguaia specimen, as well as the great
length discrepancy between the spine and the soft rays
(a common feature in most species of Ernstichthys) are
not present in any of the specimens known of E.taquari.
Also, the eyes of the Araguaia specimen are noticeably
smaller proportionally than those of E. taquari. Finally,
the particular color pattern of the Araguaia specimen
(with a thin inter-ocular bar but no trans-orbital bar and
more or less regular-sized small spots forming a speck-
led covering on head and dorsum) is also not present in
any E.taquari (although not much weight attaches to this
difference because of the wide pigmentation variation in
species of Hoplomyzontini and the limited number of
specimens available). It is impossible at this time to con-
fidently resolve the taxonomic status of the Ernstichthys
specimen from the Rio Araguaia illustrated in Jarduli
etal. (2014). Preliminary differences noted above, how-
ever, suggest that it is not conspecific with E.taquari.
Another report of Ernstichthys in the Brazilian Amazon
is provided in Ohara & Zuanon (2013) on the basis of
a single specimen from the Rio Madeira, identified as
E.cf.anduzei. As noted by the authors (p. 125), this par-
ticular specimen does not conform to E.anduzei in the
number of dentations in the pectoral-fin spine (nine; vs.
10 to 14). Also, the gentle curvature of the pectoral-fin
spine and the relatively gradual length difference be-
tween the spine and soft rays both do not match the
rather abrupt distal spine curvature and the large length
discrepancy between spine and soft rays in E.anduzei.
In both traits, the Madeira specimen approaches condi-
tions in E.taquari, an obviously more similar taxon. Like
in the preceding case, some differences exist that are in-
dicative that the two are not conspecific. First, the pale
coloration of the Madeira specimen lacks most dark pig-
mentation typical of hoplomyzontine species other than
those of Micromyzon. Barring some post mortem bleach-
ing of the specimen, this is well beyond the intraspecific
variation expected in the group. Second, its number of
pectoral-fin spine dentations (nine) is intermediate be-
tween E.taquari (7-8) and E.anduzei (10-15). Finally, the
pectoral-spine length of that specimen is 31.8%SL (mea-
sured from the published photograph), thus significantly
shorter than that of E.taquari (35-36.5%SL). The summa-
tion of those differences suggests that the specimen of
E.cf.anduzei reported in Ohara & Zuanon (2013) is not a
representative of E.taquari. As before, however, such ev-
idence is insufficient to properly resolve the question at
this time. More material and direct comparisons of spec-
imens are needed.
Geographic distribution
Ernstichthys taquari is so far known from the type lo-
cality in the rio Taquari, tributary of rio Paraguay basin
(Fig.3).
Conservation status
Ernstichthys taquari is endemic to Brazil and only
known from its type-locality at the upper Rio Taquari. Its
area of occupancy (AOO) (B2) of 4km² is based on this
only known record. The AOO is likely underestimated
since representatives of the genus are very rare in collec-
tions. As discussed above in the corresponding section
on Paracanthopoma saci, siltation of the Rio Taquari is the
most critical environmental and socio-economic prob-
lem in the Pantanal (Soriano etal., 2001). Aspredinidae
often occupy specific and rather complex microhabitats
and siltation likely extirpates the type of environments
that E. taquari likely requires. A continuing decline in
habitat quality b (iii) is inferred based on the still grow-
ing pasture areas and siltation. It is not possible to meet
subcriterion ‘a’ because the population is not necessarily
fragmented. Therefore, we suggest this species is clas-
sified as Near Threatened, close to meeting Critically
Endangered (CR) by the following criteria B2b (iii) accord-
ing to the International Union for Conservation of Nature
(IUCN) categories and criteria (IUCN, 2020).
DISCUSSION
The phylogenetic placement of Paracanthopoma saci
in Vandelliinae is supported by all synapomorphies so far
proposed for the subfamily, a very strongly-corroborat-
ed monophyletic group. Those include the dentaries not
meeting at the midline; the presence of “claw-like” teeth
in the premaxillae; the lack of the fifth ceratobranchial
and associated toothplate; the absence of hypobranchi-
als two and three; the toothless upper pharyngeal tooth-
plate; the absence of vomer; the absence of mesocora-
coid; and the fully cartilaginous fourth pharyngobranchi-
al (Baskin, 1973; de Pinna, 1998; DoNascimiento, 2012)
plus some unique myological synapomorphies (Datovo
& Bockmann, 2010). Finally, the specialized feeding on
the blood of other vertebrates, given its uniqueness, is
also valid evidence for monophyly, although one which
at this point refers to general biology rather than specific
character states.
Paracanthopoma is perhaps the most clearly-defined
genus in Vandelliinae. The integument fold across the
isthmus is an easily-observable character that occurs
nowhere else in Vandelliines and has been part of the
diagnosis of the genus since its establishment (Giltay,
1935). It is also a unique feature among its closest rela-
tives, the Stegophilinae and Tridentinae. Although nearly
all tridentines (except Miuroglanis) and some stegophil-
ines (Acanthopoma, Apomatoceros and Schultzichthys)
have superficially similar structures, they all differ from
the situation in Paracanthopoma. The membranes in
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for subsets of the genus (a discussion of this topic, in the
context of P.parva and one of the undescribed species,
is provided in DoNascimiento, 2012). Regardless of such
factors, little doubt exists that P.saci is the closest relative
of P.parva among currently-known vandelliine diversity.
Species-level distinction between P. saci and P. par-
va is well-corroborated by a series of conspicuous dif-
ferences in various body systems, as summarized in the
Diagnosis above. The distinctions are pronounced in kind
and degree, resulting in fishes with very different general
aspect and which can be distinguished at a glance with
the naked eye, despite their small size. Examination of
series of P.parva (cf., Comparative Material) plus 15 spec-
imens of P. saci demonstrate that none of those diag-
nostic characteristics is subject to intraspecific variation
sufficient to bridge the gaps between the two species.
In fact, the profound differences in body and head struc-
ture suggest species with quite different biologies. The
delicate mouth dentition of P.saci is probably associated
with a specialization on smaller hosts and perhaps subtle
approaching strategies, when compared with the brut-
ish oral armature of P.parva. Also, the spatulate caudal
peduncle is indicative of a swimming mode based on
propelling by the posterior part of the body, rather than
by undulations of the entire body. All those factors in-
dicate that considerable divergence exists between the
two species of Paracanthopoma. In fact, species diversity
of the genus is substantially larger than presently docu-
mented not only in species numbers but also in pheno-
typic divergence, as an ongoing revision of the group by
the authors confirms.
Hoplomyzontinae is a strongly-supported mono-
phyletic group. Its corroborating synapomorphies
are not only numerous and diverse, but they are also
highly conspicuous. Their body armor, for example, is
unique among aspredinids. Although some other cat-
fish groups also have a body armor, such as distal lori-
carioids (Callichthyidae, Scoloplacidae, and Loricariidae),
Doradidae, Amphiliidae (Doumeinae), and Sisoridae
(Sisor), structural details of the armor in hoplomyzon-
tines are unique. They are the only mailed catfishes
where the bony shielding is formed by a combination
of emerging vertebral expansions (dorsal and ven-
tral shield series) and independent plates formed from
modified lateral-line ossicles in the lateral series (Friel &
Lundberg, 1996). Other undisputed synapomorphies for
the subfamily include the absence of ribs, absence of
urohyal, 5+4 principal caudal-fin rays, premaxilla with an
anterior limb, the anterior displacement of the pelvic fin
and girdle so that the basipterygia lie very close to the
coracoids, partly included between coracoid processes
(Friel, 1994). Ernstichthys taquari shares all those synapo-
morphies and little doubt remains as to its placement in
Hoplomyzontinae.
The generic allocation of the new species needs
more detailed discussion because the relevant set of
evidence is less decisive than that for the subfamily lev-
el. The long pectoral-fin spine is the most visible simi-
larity that E.taquari shares with other species currently
in Ernstichthys. This is clearly an apomorphic condi-
Tridentinae are actually free branchial membranes, with
completely embedded branchiostegal rays and not at-
tached to the isthmus (or only narrowly attached ante-
riorly), leaving a large unconstricted branchial opening.
In stegophiline taxa mentioned above, the membrane is
broadly attached to the isthmus (a condition general in
the clade consisting of Stegophilinae and Vandelliinae,
none of which has free branchiostegal membranes) and
the free flap is clearly a portion of the membrane poste-
rior to the fusion, because it contains embedded bran-
chiostegal rays. The situation is easily verified in alcoholic
or c&s material by lifting the membrane and observing
the totally included set of rays in the free flap. The struc-
ture is very different in Paracanthopoma. Here, the free
fold does not consist of a free branchiostegal membrane,
contrary to reported in the original description of the
genus (Giltay, 1935) and repeated in several subsequent
publications and keys. The actual branchiostegal mem-
brane in Paracanthopoma is nearly entirely fused to the
isthmus, leaving the branchial opening reduced to a
small passage limited to the region between the opercu-
lar and interopercular patches of odontodes, as in all oth-
er vandelliines. The integument fold across the isthmus
in Paracanthopoma is actually an independent structure
that overlays the whole isthmal region. It contains no
branchiostegal rays, which are located entirely in the soft
tissue anterior to the fusion with the isthmus. The fold
forms a broad and deep integument flounce extending
continuously across the isthmus, with no embedded
rays. The Paracanthopoma fold is probably a derivative
of the branchiostegal membrane, but constitutes a set
of specialization exclusive to the genus. In order to high-
light its neomorphic nature and avoid further confusion
with the branchiostegal membrane itself, here we call it
a branchiostegal velum.
Comparative examination of the anatomy of
Paracanthopoma reveals other putative synapomorphies
for the genus in the skeleton. For example, species of the
genus (including all new taxa known to us) have a dis-
tally bifurcated maxilla, a unique configuration among
the otherwise single-headed maxillas of other vandel-
liines and trichomycterids in general. Their median pre-
maxilla is also different from that of all other vandelliines
and stegophilines (the only taxa having that structure)
in having bilateral dorsal flanges bracing the neck of the
mesethmoid immediately posterior to the mesethmoid
cornua. The median premaxilla in other taxa lacks an
elaborate dorsal surface of that bone (a non-homolo-
gous median process is present in most stegophilines).
A complete phylogenetic evaluation of Paracanthopoma
lies beyond the scope of the present paper, but a hypoth-
esis of its monophyly is well-supported by a few unique,
uncontradicted and well-defined character conditions
(in addition to the characters above, an additional list
is provided in DoNascimiento, 2012, not explicitly enu-
merated here because that work is still unpublished). Of
course, not all unique characteristics shared between
P.saci and P.parva will necessarily be synapomorphic for
the entire genus once its species diversity is more com-
pletely mapped, because some will be synapomorphic
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tion. Other hoplomyzontines allocated in Hoplomyzon,
Micromyzon, and Dupouyichthys have a proportionately
much shorter spine, similar in that regard to that in oth-
er aspredinids and catfishes in general. Although the
pectoral-fin spine in E.taquari is more similar to that of
congeners than to that of other genera in the subfam-
ily, it is also noticeable that its condition is the least ex-
treme in the genus. Other species of Ernstichthys have
a comparatively longer and more distally curved spine,
approximately twice as long as the rest of the fin. Also, in
E.taquari the size discrepancy between the pectoral-fin
spine and remaining fin rays is not as dramatic (Figs.4-5).
Thus, the situation of the pectoral fin in E.taquari is inter-
mediate between the state in other Ernstichthys, on the
one hand, and the one in remaining hoplomyzontines,
on the other. Friel (1994) lists as an unambiguous synapo-
morphy for Ernstichthys an expanded and distally-flared
transverse process of the fifth vertebra, different from the
thin and evenly wide process of other hoplomyzontines.
Ernstichthys taquari clearly shares the distally expanded
transverse process of the fifth vertebra (Fig.6A).
A few other characteristics are corroborative of that
allocation, although they must be considered as provi-
sional at this point because relevant comparative infor-
mation is not available for all hoplomyzontine species.
For example, the shape of the coracoid process, broad
for most of its length and then pointed at the tip, is very
similar in E. taquari and other Ernstichthys species (cf.,
Taphorn & Marrero, 1990: fig.2C) and different from the
blunt, medially-curved shorter process in other hoplo-
myzontine genera (cf., Taphorn & Marrero, 1990: fig.2A;
Carvalho etal., 2016: fig.4A; Carvalho etal., 2017: fig.4A).
It also deserves notice that the structure of the basipte-
rygium in E. taquari is very similar to those of at least
some other congeneric species, with a broadly-triangular
anterior arm directed straight towards the posterior sur-
face of the coracoid (cf., Taphorn & Marrero, 1990: fig.2C).
This is different from the condition in hoplomyzontines
allocated in other genera, where the anterior arm of the
basipterygium is very short and poorly differentiated
from the rest of the bone, or narrow and directed antero-
laterally (cf., Taphorn & Marrero, 1990: fig.2A; Carvalho
etal., 2016: fig.10, 2017: fig.10).
Much weight has been given to so-called preanal
bony “plates” (actually not always true plates, see above)
in hoplomyzontine taxonomy, which are serially posi-
tioned, medially and bilaterally, anterior to and along-
side the base of the anal fin. Those shield series are in fact
morphologically heterogeneous, some shields formed
by expanded median vertebral processes or hemal
spines, others by lateral vertebral processes, and finally
some from anal-fin pterygiophores. It has been noted
that much intraspecific variation exists in the morphol-
ogy of those shields (Friel & Lundberg, 1996:647) and
much of that variation remains uncharted. A majority of
the shields are just the endpoints of much larger internal
structures that reach the surface of the integument. Part
of the observed variation, both intra- and inter-taxonom-
ically, is a result of whether or not, and to what degree,
the terminal structures emerge at the surface. Despite
such caveats, some information from the preanal shields
is certainly useful taxonomically and, if properly studied,
helps to further test the generic affinities of E. taquari.
The anteriormost preanal shield is a median vertebral
derivative formed from a distally expanded hemal spine
(see Description above). In E. taquari, that shield is as
long as broad or slightly longer than broad, has long di-
verging arms anteriorly (around the anal and urogenital
openings area) and its anterior and posterior margins are
strongly concave. This is the same overall shape seen in
E.anduzei and E.megistus, but not in E.intonsus, where it
is arc-shaped, much broader than long, concave anteri-
orly and convex posteriorly (cf., Stewart, 1985: figs.1D-F;
Taphorn & Marrero, 1990: fig.3C). Although not present
in all species currently in Ernstichthys, the peculiar shape
of the first preanal shield is not present in any other hop-
lomyzontine, thus constituting valid evidence of rela-
tionships. The second (middle) shield, also a hemal spine
derivative, is long and narrow in E.taquari, E.megistus
and E.intonsus, but in E.anduzei it is variable, either long
as in congeners or roundish (Stewart, 1985:15). The mid-
dle preanal shield is also somewhat elongate in M.aka-
mai (Friel & Lundberg, 1996: fig.4) but not to the same
degree as in species of Ernstichthys listed above.
The dorsal and ventral bony shield series in all spec-
imens known of Ernstichthys taquari differ from those of
all congeners in being comparatively narrow, thus failing
to overlap or contact each other along most of the two
series except the posterior, medially-united elements. In
most other hoplomyzontines, the plates contact or even
broadly overlap their neighbors. This trait in fact differen-
tiates E.taquari from all other hoplomyzontines except
species of Hoplomyzon, which also have narrow, non-con-
tacting dorsal and ventral shields. However, details of the
shape of the plates differ in E.taquari and Hoplomyzon
species. In Hoplomyzon, the shields are roundish and
symmetrical in shape (Carvalho etal., 2017). In E.taquari,
contrastingly, the respective plates are roughly triangu-
lar and slanted posteriorly. This detail approaches the
condition in E.taquari to that in its congeners, regardless
of the discrepant non-overlapping condition. In fact, the
situation of the dorsal and ventral shields in the species
seems like an attenuated form of that in other species of
Ernstichthys.
Ernstichthys taquari also shares characters states at
more inclusive clades within hoplomyzontines that in-
clude the hypothesized closest relatives of its genus.
For example, the species lacks premaxillary and den-
tary teeth, like Dupouyichthys, Micromyzon, and other
Ernstichthys. The significance of this trait, however, is not
as decisive as it once was, because Hoplomyzon cardosoi
also lacks teeth on both bones (Carvalho etal., 2017).
Naturally, a decision about the generic allocation of
Ernstichthys taquari depends not only on positive evi-
dence for its alignment with Ernstichthys, as done above,
but also on the lack of evidence for alternative place-
ments. Accordingly, the species was investigated as to
the presence of diagnostic characters so far proposed
for other hoplomyzontine genera. Hoplomyzon has
been diagnosed by many characteristics in various pub-
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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lications, however a recent reevaluation (Carvalho etal.,
2017:12-13) concluded that a single characteristic is ac-
tually apomorphic and confirmed in all species of the ge-
nus: the presence of large well-defined papillae disposed
along the margin of the upper jaw. This is a trait which
has been traditionally used to diagnose the genus since
its description (Myers, 1942) and which is not present in
any species of Ernstichthys, including E.taquari.
The genus Dupouyichthys, with its single species,
D. sapito, is the least known hoplomyzontine genus.
The configuration of the preanal plates in D.sapito was
considered as synapomorphic for the genus by Stewart
(1985) while Friel (1994) considered the presence of a
single such pair as equally diagnostic. To that it might
be added that the club-shape and orientation of the
bilateral shields on each side of the first (median) pre-
anal plate (Stewart, 1985: fig.1C) are also unique among
hoplomyzontines. The same probably also holds for the
rough lozenge shape of the first and second preanal
shields in the species (with reservations about possible
yet unmapped intraspecific variation). In any event, none
of those particularities typical of Dupouyichthys are pres-
ent in E. taquari. The fourth and final hoplomyzontine
genus, Micromyzon, has recently been phylogenetically
rediagnosed in Carvalho et al. (2016) by the following
traits: eyes absent; lateral margin of frontal straight, not
forming an orbital concavity; posterior cranial fontanel
reduced or absent; premaxilla absent or extremely re-
duced; limb of autopalatine posterior to lateral ethmoid
articulation about one fourth the length of anterior limb;
rows of large tubercles absent along posterior lateral
line; dark integumentary pigmentation reduced or ab-
sent. Except for the orbital concavity character, which
is present (albeit reduced) in the specimen examined
of M. akamai, all other characters are consistent with
the observations made in association with this paper.
As before, E.taquari lacks each and all of those putative
Micromyzon synapomorphies. In sum, E.taquari does not
bear any convincing character evidence for its inclusion
either in Hoplomyzon, Dupouyichthys or Micromyzon.
Therefore, the anatomy of E. taquari not only provides
evidence that is the closest relative of species currently
allocated in Ernstichthys, but also reveals no evidence for
alternative generic placements.
Biogeographic framework
Ernstichthys taquari is the first Hoplomyzontinae spe-
cies reported for the southern half of South America. The
subfamily is otherwise a typical component of northern
basins of the continent, with nearly its entire diversity
in the Amazonas-Orinoco (Fig.3). The presence of the
genus Ernstichthys in the rio Paraguay basin and in the
rio Araguaia basin (Jarduli etal., 2014), is congruent with
the pattern proposed for the group in Dagosta & de
Pinna (2019). In that paper, Ernstichthys was one of the
examples corroborating the pattern called “Cis-Andean
Foothills”, composed of taxa with distributions restricted
to the uplands of the western region of South America,
mainly in basins draining the Andean region. In addition
to the examples by Dagosta & de Pinna (2019), other
corroborative taxa include Gephyrocharax (Ferreira etal.,
2018), Brycon hilarii and B.whitei (Lima, 2017) and the
siluriforms Lamontichthys (Paixão & Toledo-Piza, 2009),
Otocinclus huaorani (Schaefer, 1997), O.vittatus (Schaefer,
1997), Pimelodella howesi (Slobodian, 2017), and Rhamdia
poeyi (Silfvergrip, 1996). The Cis-Andean Foothills distri-
bution pattern forms an arc with the concavity directed
towards the Amazonas-Orinoco (Dagosta & de Pinna,
2019: fig. 21a). The extension of the arc varies among
taxa, mainly in its southern and eastern reaches. Some of
those groups have a presence also in the Paraná-Paraguay
(e.g., Astyanacinusspp. – here considered as a valid ge-
nus – Brycon hilarii, Gephyrocharaxspp., Leporinus stria-
tus, Rhyacoglanisspp.), or Tocantins (Lamontichthysspp.,
Rhamdia poeyi, Xyliphiusspp.), although most examples
have their southern limit in tributaries of the rio Madeira.
As hypothesized by Vari (1988), it is likely that species
with that pattern of distribution are limited by ecolog-
ical requirements associated with swiftly flowing rivers.
Indeed, species of Ernstichthys have been included in the
guild of rheophilic fishes by Lujan & Conway (2015). The
type locality of Ernstichthys taquari is also the source of
the first record of the genus Paracanthopoma (Fig.3; re-
cords for the genus from material directly examined for
this study plus data on undescribed species from an on-
going revision of Vandelliinae by the authors) outside of
the Amazonas-Orinoco axis. Ernstichthys clearly has a Cis-
Andean Foothills distribution associated with highlands.
Contrastingly, Paracanthopoma is a lineage broadly dis-
tributed in the Amazonas-Orinoco, with both highland
and lowland species (most yet undescribed).
Though exceptional, the presence of those two typ-
ically Amazonian lineages (Fig.3) in a tributary of the
Pantanal Wetland is not unique. It has been known for
a long time that the headwaters of the Rio Paraguay
include some odd Amazonian components, usually re-
stricted in distribution (Lima et al., 2007; Ribeiro et al.,
2013; Lopes etal., 2020). The ecological barrier represent-
ed by the Pantanal Wetland prevented such upper-wa-
ter course, clear water, high-energy, components from
spreading to the rest of the basin, thus explaining their
narrow endemism. The presence of Ernstichthys taquari
and Paracanthopoma saci are eloquent additional ele-
ments in that pattern.
The lack of a phylogenetic hypothesis for species of
Ernstichthys and Paracanthopoma (as mentioned above,
there are several undescribed species in the genus)
is not a full impediment in understanding the gener-
al features of their associated biogeographic history.
Important parts of that history can be inferred from
ancestral biogeographic reconstructions based on the
phylogenetic position of the genera in their respective
families. The two genera are exclusively Amazonian, al-
though their sister genera are not: Parandellia in the
case of Paracanthopoma and Dupouyichthys in that of
Ernsticthys.
Ancestral biogeographic reconstruction from the
BBM model (Fig.7A,D) indicates that the two new spe-
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
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cies likely arrived secondarily in the Paraguay basin from
the Amazonas-Orinoco-Guiana. Model S-DIVA on the
other hand, results in a 50% probability that Ernsticthys
taquari is in the rio Paraguay basin by geodispersal, com-
ing from the Amazonas-Orinoco-Guiana and 50% that
its presence there is the result of vicariance (Fig. 7B).
Figure7. Ancestral geographic reconstruction from Aspredinidae using BBM (7A) and S-DIVA (7B) and from the MTSVG clade of Trichomycteridae using S-DIVA (7C)
and BBM (7D). Biogeographical regions: A= Amazon-core; B= São Francisco and Eastern Coastal drainages; C= Paraná-Paraguay; D= Trans-Andean. Black arrows
indicate biotic dispersal from Amazon-core to Paraná-Paraguay region. See Materials and Methods section for further analytic details.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
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Resolution of that uncertainty must await resolution of
the phylogenetic position of the species among other
species of Ernstichthys. In the case of Paracanthopoma
saci, S-DIVA infers that its presence in the Paraguay re-
sults from vicariance, on the occasion of its separation
from the Amazonas-Orinoco-Guiana (Fig. 7C). Because
several species of Paracanthopoma await description
(MdP, pers.obs.) all of which from the Amazonas-Orinoco-
Guiana region, this biogeographic scenario will be tested
once more taxa are included in the analysis. Again, the
phylogenetic position of P.saci in its genus is key to a res-
olution of the question.
Despite some degree of uncertainty, a majority of
resolutions support the hypothesis that both Ernsticthys
taquari and Paracanthopoma saci reached the Paraguay
secondarily, from Amazonian ancestors. Although an op-
posite scenario is theoretically possible (i.e., that those
genera arose in the Paraguay and subsequently colo-
nized the Amazon), such hypothesis requires multiple
cases of lineage extinction in the Paraguay and is not
supported by any of the results. The unlikeliness of such
idea is compounded by the fact that the Paraguay is by
no means a depauperate basin in terms of fish species
and lineages (Fig.7).
The occurrence of both Ernstichthys and
Paracanthopoma exclusively in the upper rio Taquari may
suggest a biogeographical history separate from other
tributaries of the Paraguay system, even if the acquisi-
tion of these Amazonian components is not necessarily
related with a single biogeographical event (i.e., they are
not necessarily biographically homologous). The Taquari
river basin is therefore a hybrid biogeographical unit,
with part of its ichthyofaunistic composition related to
the Paraguay river basin, of which it is currently tribu-
tary, and part associated to past connections with the
Amazon.
Both Ernstichthys and Paracanthopoma are absent in
neighboring tributaries of the rio Paraguay and upper rio
Paraná, but present in the rio Araguaia, an Amazonian
tributary. This places the latter basin as a prime candi-
date for potential faunal exchange with the Taquari ba-
sin. The physical proximity between the headwaters of
the rio Taquari with its neighboring Amazonian basins is
extreme (Fig.8), in some cases only a few hundred me-
ters. It is intuitively obvious that headwater stream cap-
ture resulted in the presence of Amazonian elements in
the upper rio Taquari. Such events are often associated
with the upper reaches of adjacent basins and is largely
responsible for the historically reticulate nature of riv-
er drainages (Lima & Ribeiro, 2011; Ribeiro etal., 2013;
Dagosta & de Pinna, 2017) (Fig.8).
The region where both Ernstichthys taquari and
Paracanthopoma saci were collected in the upper rio
Taquari is located close to the Trans-brazilian lineament,
a major geological suture zone where Precambrian faults
have been reactivated during the Paleozoic, Mesozoic,
and Cenozoic (Paranhos-Filho et al., 2013). Such reac-
tivations are known to have caused the formation of
the Pantanal (Assine & Soares, 2004), with wide-scale
hydrological reorganization and rampant headwater
capture events in adjacent uplands (Ribeiro etal., 2013).
Topography shown in Fig.3 clearly shows that the up-
per rio Taquari is located at the border of the Pantanal
Wetland depression and the presence of Ernstichthys
taquari and Paracanthopoma saci are possible additional
elements in that pattern.
Conservation of a highly endemic, poorly
known and threatened region
The two new species herein described are from the rio
Taquari, a river which is part of the Pantanal Wetland sys-
tem but which drains an area of Cerrado biome where the
species were collected. The locality is part of the region
delimited and named by Dagosta etal. (2020) as “Upper
Araguaia”. The region corresponds to the uppermost part
of the rio Araguaia drainage, upstream of various water-
falls and rapids such as the falls of Couto Magalhães at
Santa Rita do Araguaia (State of Goiás). Despite its name,
the “Upper Araguaia” bioregion includes also headwaters
of tributaries of the Paraguay basin, as the rio Correntes
and the rio Taquari, which drain the eastern limit of the
Pantanal Wetland.
In addition to the two species herein reported, a num-
ber of other fish endemics occur in the Upper Araguaia
bioregion, such as Astyanax joaovitori, Characidium
chicoi, Cyphocharax boiadeiro, Eigenmannia correntes,
Hyphessobrycon eilyos, H. langeanii, H. weitzmanorum,
Aspidoras velites, A. taurus, Cnesterodon septentrionalis,
Melanorivulus litteratus, M. urbirajarai, Simpsonichthys
cholopteryx and other three species of Characidae yet
undescribed (F. Dagosta, pers.comm.). This density of en-
demics is the main factor accounting for the delimitation
of that area as a biogeographically distinct unit in the an-
alytical estimates implemented by Dagosta etal. (2020).
In fact, it is one of the smallest fish bioregions recog-
nized in South America. Besides its small area and abun-
dance of endemics, the Upper Araguaia bioregion was
highlighted by the authors as an Endemic Amazonian
Figure8. Water divide between upper Paraguay (black rivers), upper Paraná
(blue rivers), and upper Araguaia (white rivers). Gray dash-line represents
the Trans-brazilian lineament. Thin yellow dashed line means water divide
boundaries between neighbouring basins. Black star shows type locality of
Ernstichthys taquari and Paracanthopoma saci.
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper ParaguayPap. Avulsos Zool., 2021; v.61: e20216147
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Fish Area (EAFA) with priority for conservation. That
qualification is based on the scarcity of protected areas
in the region, the presence of threatened species (e.g.,
Melanorivulus litteratus and M. urirajarai), and – mainly
– deforestation pressure and dam construction. The two
latter threats are particularly severe in hydrographic ba-
sins draining the Cerrado biome, were a major portion of
the agribusiness output and electricity generation is lo-
cated in Brazil (Latrubesse etal., 2019). The region where
Paracanthopoma saci and Ernstichthys taquari were col-
lected has large-scale cattle farming as the main econom-
ic activity. On the other hand, the “Amazonian” portion of
the “Upper Araguaia” bioregion has a predominance of
large monocultures such as cotton and sugar cane. The
entire bioregion is dotted with planned small hydroelec-
tric dams, some of which already in place. Therefore, mul-
tiple factors demonstrate the Upper Araguaia bioregion
is in imminent danger of major biodiversity loss and ur-
gently requires conservation measures.
Finally, it is remarkable that the rio Paraguay basin is
considered as a relatively well-sampled system, with a
well-known fish fauna. The discovery of such conspicu-
ous elements as the new species herein reported demon-
strates that fish biodiversity in the Paraguay drainage
and in central Brazil is still underestimated.
Comparative material
Hoplomyzontinae: Micromyzon akamai, MZUSP 48550,
1 ex, holotype, Brazil, Pará, Rio Tocantins, above con-
fluence with Rio Pará (01°50′S, 49°17′W), col. A. Akama
etal., 20Nov1994; MZUSP 48551, 3ex, paratypes, col-
lected with holotype; MZUSP 48552, 1ex, paratype, c&s,
Brazil, Pará, Rio Amazonas, south side of river, across
from Monte Alegre, ca.52km downriver from mouth of
Rio Tapajós (02°01′S, 54°05′W), col. A. Akama, A. Zanata,
04Nov1994. Ernstichthyssp. MZUSP 37814, 7ex (1c&s),
Brazil, Mato Grosso, Igarapé Ingazeiro, 20km upstream
from mouth of Rio Canumã on Rio Ariuanã, below
Dardanelos (Rio Madeira basin) (09°58′S, 59°19′W), col.
Joint MZUSP/INPA expedition, 17 Nov 1976; MZUSP
74184, 1ex, Brazil, Amazonas, Rio Madeira, col. A. Zanata
et al. Hoplomyzon sexpapilostoma, MZUSP 38894, 5 ex,
paratypes, Venezuela, Barinas, Río Masparro, col. D.
Taphorn, C. Lilyestrom, 13Nov1983.
Trichomycteridae, Stegophilinae (all from Brazil):
Acanthopoma annectens, MZUSP 55706, 2ex, Amazonas,
Rio Solimões, col. J. Lundberg et al., 12 Nov 1993.
Apomatoceros alleni, INPA 16695, 1 ex, Amazonas, Rio
Solimões, Costa da Terra Nova, Lago Castanho, col. M. de
Pinna and L. Py-Daniel, 19Mar2001. Schultzichthys bondi,
FMNH 105572, 31ex, Ecuador, Rio Napo at Coca, col., D.
Stewart and M. Ibarra, 01Oct1981.
Trichomycteridae, Tridentinae: Miuroglanis platycepha-
lus, MZUSP 7805, 3ex (1c&s), Brazil, Amazonas, Parintins,
col. Expedição Permanente da Amazônia. Tridens mela-
nops, INHS 40467, 3 ex, Peru, Loreto, Río Nanay (Río
Amazonas drainage), col. B.M. Burr etal., 09 Aug 1996.
Tridentopsis cahuali, MNHNP 1448, 12 ex, Paraguay,
Presidente Hayes, Pozo Colorado, col., O. Romero etal., 20
Apr 1996. Tridentopsis pearsoni, CAS 56200, 3ex, Bolivia,
Beni, Lake Rogoagua, col. N.E. Pearson.
Trichomycteridae, Vandelliinae: Paracanthopoma par-
va. Brazil: IRSNB 10121, 2 ex, holotype and paratype,
Brazil, upper Rio Catrimani (Rio Branco drainage), col. C.
Lako; CAS 118205, 1ex, Amazonas, upper Rio Catrimani
(Rio Branco drainage), col. S. Lako; INPA 16555, 2 ex
(1 c&s), Roraima, Boa Vista, Maracá, Rio Branco, col. O.
Bitar, May 1988; MZUSP 30400, 10ex (3c&s), Rondônia,
Independência, main channel of Rio Machado (Rio
Madeira drainage), col. M. Goulding, 06May1978; MZUSP
29793, 2ex, Amazonas, Rio Negro at Cachoeira de São
Gabriel, col. M. Goulding, 18May 1979; MZUSP 63076,
25 ex (4 c&s), Mato Grosso, Nova Mutum, Rio Arinos
(Rio Tapajós drainage), col. H.F. Mendes, 16 Jan 1998;
MZUSP 40585, 29 ex (5 c&s), Goiás, Monte Alegre de
Goiás, Rio Paraná above the mouth of Rio Bezerra (Rio
Tocantins drainage), col. J.C. de Oliveira & W.J.E.M. da
Costa, 10Jan 1989; MZUSP 74624, 13 ex, Mato Grosso,
Rio Xingu, Parque Indígena do Xingu, Posto Diauarum,
col. G.R. Kloss, 08 Dec 1973. Ecuador: FMNH 99519,
2ex, Río Aguarico, near Destacamento Militar Cuyabeno
and confluence of Río Cuyabeno and Río Aguarico
(Río Napo drainage), col. D. Stewart etal., 21 Oct1983.
Guyana: ANSP 179207, 2ex, Rupununi (Region9), Ireng
River, 6.9km WSW of village of Karasabai (04°01′10″N
59°36′06″W), col. M.H. Sabaj et al., 01 Nov 2002. Peru:
MUSM 4562, 3ex Madre de Dios, Parque Nacional Manu,
Manu, Pakitza, Río Manu, col. H. Ortega, 22 Jun 1993.
Paravandellia oxyptera. MZUSP 9597, 1 ex, Brazil,
Amazonas, Anamã, Rio Solimões, col. EPA, 21Sep 1968;
MZUSP 23352, 1 ex, Brazil, Amazonas, Rio Solimões, in
front of Jacaré, near Fonte Boa, col. EPA, 07Oct 1968;
MZUSP 83703, 8ex (2c&s), São Paulo, São Carlos, Ribeirão
das Araras (Rio Grande drainage), col. J.L. Birindelli etal.,
09Oct2002; MZUSP 89973, 1ex, Mato Grosso, Tangará da
Serra, Rio Sepotuba, below Salto das Nuvens (14°37′15″S,
57°44′20″W), col. H.A. Britski etal., 09Mar2002; MZUSP
90600, 2ex, Mato Grosso, Cáceres, Rio Sepotuba (middle
course) (Rio Paraguai drainage) (15°24′37″S, 57°42′20″W),
col. H.A. Britski etal., 04Mar2002; MZUSP 106061, 6ex,
Amazonas, Río Mavaca (Río Orinoco drainage), beach up-
stream from base-camp of Tapirapecó Expedition, col., R.
Royero etal., 22Mar1988.
ACKNOWLEDGMENTS
We thank Alexandre Ribeiro who provided valu-
able suggestions during development of this paper.
The manuscript benefitted greatly from reviews by
C. DoNascimiento and T. Carvalho. We are grateful to
Anderson Ferreira, Manoela Marinho, Osvaldo Oyakawa,
Priscila Camelier, and Ricardon Zanon for their help in
fieldwork. F.C.P.D. thanks Anderson Ferreira, Fabiano
Antunes, Márcia Regina Russo and Adnara Ribeiro
Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147
21/23

Gomide for administrative support at UFGD, MS and
Bruna Barbosa (Prefeitura de Alcinópolis), Erciliomar
Furquim Rocha (Prefeitura de Alcinópolis) and Sandro
Menezes Silva (UFGD, MS) for logistical support in the
field. We thank V. Reis and C. DoNascimiento for many
discussions on trichomycterid evolution and systemat-
ics. V. Reis also made photographs used in figs.1and4.
Authors are partially funded for field activities to collect
fish specimens by the Fundação de Amparo à Pesquisa
do Estado de São Paulo – FAPESP, http://www.fapesp.
br (F.C.P.D. #2016/19075-9; M.P. #2015/26804-4) and by
the Conselho Nacional de Desenvolvimento Científico
e Tecnológico – CNPq, http://www.cnpq.br (F.C.P.D.
#405643/2018-7; M.P. #310688/2019-1).
AUTHORS’ CONTRIBUTIONS
F.C.P.D., M.P.: Conceptualization, Methodology,
Software, Data curation, Formal analysis, Writing – orig-
inal draft, Visualization, Investigation. Writing – review
& editing. All authors actively participated in the discus-
sion of the results, and reviewed and approved the final
version of the paper. Authors declare no conflict of inter-
est related to this paper.
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