Non-technical Summary
Malacostracan crustaceans such as crabs, shrimps, and isopods are very diverse today with over 43,500 species living in marine, freshwater, and terrestrial environments. Their fossil record, which spans about 500 million years, remains understudied for many groups. One group of malacostracans, the Belotelsonidea, are crustaceans with a shrimp-like body shape only found in rocks from the Carboniferous Period (ca. 360–300 million years ago). We describe the fourth species of this group, Lobetelson feldmanni new species, from ca. 305-million-year-old shales of the Kinney Brick Quarry, New Mexico, USA. The description is based on the holotype specimen, which is relatively complete, flattened, and with an eye preserved. A second specimen from the same locality might belong to L. feldmanni n. sp., but that specimen is insufficiently preserved to be certain. This species represents the youngest record of Belotelsonidea, a group that survived for ca. 40 million years. Belotelsonids have been found only in Scotland and various parts of the USA during the Carboniferous, when those parts of the world were located between the equator and ~20° south. Most individuals lived in the shallow oceans, but the oldest ones may also have lived in brackish–freshwater environments.
Introduction
Today, Malacostraca Latreille, Reference Latreille1802, are the most diverse crustaceans with over 43,500 species inhabiting marine, freshwater, and terrestrial environments (e.g., Ahyong, Reference Ahyong, Poore and Thiel2020; Bernot et al., Reference Bernot, Owen, Wolfe, Meland, Olesen and Crandall2023). The earliest fossil malacostracans are known from the Cambrian (e.g., Collette and Hagadorn, Reference Collette and Hagadorn2010; Ahyong, Reference Ahyong, Poore and Thiel2020). Whereas malacostracan diversity increased somewhat in the middle Paleozoic due to a rise in phyllocarids (Sepkoski, Reference Sepkoski2000; Schram and Koenemann, Reference Schram and Koenemann2021), malacostacans became much more diverse during the Mesozoic when decapods radiated (Sepkoski, Reference Sepkoski2000; Klompmaker et al., Reference Klompmaker, Schweitzer, Feldmann and Kowalewski2013; Schweitzer and Feldmann, Reference Schweitzer and Feldmann2015). The relationships among early groups of malacostracans have not been fully resolved (Schram and Koenemann, Reference Schram and Koenemann2021), in part because of the lack of specimens and incomplete preservation. One extinct malacostracan group is the order Belotelsonidea Schram, Reference Schram1981a, known only from the Carboniferous. The goals of this paper are to describe the stratigraphically youngest species of Belotelsonidea and to provide an overview of the species within this clade.
Geological setting
The two belotelsonid specimens studied herein originate from the Upper Pennsylvanian (Kasimovian) Tinajas Member of the Atrasado Formation in the Kinney Brick Quarry Lagerstätte, Manzanita Mountains, Tijeras, New Mexico, USA (35.00°, −106.34; WGS84). The horizon in which the holotype and other specimen were found (Unit 3) is a mudstone characterized by the exceptional preservation of soft-bodied animals, a dark color, and a lack of bioturbation, suggesting deposition occurred in anoxic conditions with poor circulation at a water depth below storm-wave base (Schneider et al., Reference Schneider, Legler, Brosig, Krainer and Lucas2021). A pteridosperm-dominated plant assemblage indicates significant freshwater input. Other taxa found in Unit 3 include a eurypterid (Braddy et al., Reference Braddy, Lerner and Lucas2023), sharks (Hodnett et al., Reference Hodnett, Grogan, Lund, Lucas, Suazo, Elliott and Pruitt2021), arachnids (Dunlop et al., Reference Dunlop, Wang, Selden and Krautz2014; Selden, Reference Selden2021), and temnospondyls (Werneburg et al., Reference Werneburg, Schneider and Lucas2021). Schneider et al. (Reference Schneider, Legler, Brosig, Krainer and Lucas2021, fig. 3B, table 2) showed and described fishes, coprolites, the bivalve Dunbarella Newell, Reference Newell1938, conchostracan branchiopods, gastropods, brachiopods, ostracods, one trilobite specimen, seeds, and megaflora from the same unit.
The same quarry has yielded two other malacostracan arthropods from different clades: Uronectes kinniensis Schram and Schram, Reference Schram1979 (order Anaspidacea), and Aenigmacaris minima Schram and Schram, Reference Schram1979 (order Aeshronectida) (Schram and Schram, Reference Schram1979; Lerner and Lucas, Reference Lerner and Lucas2021). Uronectes kinniensis is also found in Unit 3 (Lerner and Lucas, Reference Lerner and Lucas2021), whereas the horizon of A. minima was not reported (Schram and Schram, Reference Schram1979). Werneburg et al. (Reference Werneburg, Schneider and Lucas2021, p. 447) mentioned possible examples of these two taxa preserved as stomach content of a temnospondyl, also from Unit 3.
Materials and methods
Two new specimens collected in 2018 by Tom Suazo (holotype) and in 2020 by Amanda Cantrell-Suazo (other specimen) are the basis for this study. Both compressed specimens were discovered using a masonry hammer and a chisel during an excavation of fossil plants. The specimens were photographed using a Canon EOS 90D camera body with a 60 mm macro lens within an Ortech Photo-e-Box Plus with lights from both sides and the back. We also photographed the holotype under UV-A light using the same camera, not yielding additional morphological details. Other images were taken in plain sunlight with a Panasonic DMC-FZ300 camera. Anatomical abbreviations: a1 = antennula; a2 = antenna; pl1–pl5 = pleopods 1–5; s1–s6 = pleonal somites 1–6.
Repository and institutional abbreviation
Alabama Museum of Natural History paleontology collection, University of Alabama, Tuscaloosa, Alabama, USA (ALMNH:Paleo:).
Systematic paleontology
Class Malacostraca Latreille, Reference Latreille1802
Order Belotelsonidea Schram, Reference Schram1981
Family Belotelsonidea Schram, Reference Schram1974
Diagnosis
Well-developed carapace free from thoracic segments, covering thorax, with a well-developed optic notch and large lateral branchiostegal expansion; no maxillipeds, all eight thoracopods with robust endopods, without exopods; pleopods as biramous flaps, uropodal rami large and variously developed; telson longer than wide, narrowing distally, with limited subterminal lobes (from Schram, Reference Schram2006, p. 278; see also Schram and Koenemann, Reference Schram and Koenemann2021, p. 259).
Remarks
A number of specimens from the Mississippian (upper Serpukhovian) Bear Gulch Limestone in Montana, USA, were attributed to Belotelson magister (Packard, Reference Packard1886) (Schram and Horner, Reference Schram and Horner1978; Factor and Feldmann, Reference Factor and Feldmann1985; Table 1). Schram (Reference Schram2006) commented that the specimens in Factor and Feldmann (Reference Factor and Feldmann1985) differ morphologically from B. magister found at the type locality (Mazon Creek, Illinois) (Carbondale Formation, Francis Creek Shale Member), based on details in the rostrum, pleomeral pleura, telson, and on the carapace. Schram and Koenemann (Reference Schram and Koenemann2021) referred to these specimens as a probable different species. These specimens are ca. 15 million years older than B. magister from the type area, making conspecificity unlikely. Thus, we suggest that these specimens deserve renewed attention in a future study.
Table 1. Occurrences of Belotelsonidea spp. Additional references used to refine and/or infer stratigraphy and paleoenvironment: Schram (Reference Schram1981b), Dean et al. (Reference Dean, Browne, Waters and Powell2011), Lund et al. (Reference Lund, Greenfest-Allen and Grogan2015), and Mann and Maddin (Reference Mann and Maddin2019).
Table 2. Differences between taxa within Belotelsonidea. Descriptions and illustrations used: Briggs and Clarkson (Reference Briggs and Clarkson1985), Packard (Reference Packard1886), Peach (Reference Peach1881, Reference Peach1908), and Schram (Reference Schram1974, Reference Schram1979, Reference Schram2006).
Genus Lobetelson Schram, Reference Schram2006
Type species
Lobetelson mclaughlinae Schram, Reference Schram2006, by monotypy.
Other species
Lobetelson feldmanni n. sp.
Diagnosis
Rostrum length approximately equal to carapace length. Thoracopodal endopods long, thin, slit-like, with propodus extremely long. Pleonal somite 6 long compared to other somites. Uropodal rami lobate, apparently thin and not well sclerotized (modified herein after Schram, Reference Schram2006).
Remarks
Some changes were made to the original genus diagnosis. Unlike in the original diagnosis, we do not refer to size (“moderate to small” in Schram, Reference Schram2006, p. 282) because the total length of the holotype herein is substantially greater (~92 mm) than the figured specimen of Lobetelson mclaughlinae (~70 mm in Schram, Reference Schram2006, fig. 3A). The rostrum was mentioned to curve gently upward for L. mclaughlinae (Schram, Reference Schram2006), but it is straighter in the new species. Pleonal somite 6 is proportionally long in both species compared to other somites and compared to other belotelsonids, so this character was added.
Lobetelson feldmanni new species
Figures 1, 2, 4.1, 5.7; Supplementary data
Figure 1. Lobetelson feldmanni n. sp. from the Pennsylvanian (Kasimovian) Atrasado Formation (Tinajas Member, Unit 3B) of the Kinney Brick Quarry, New Mexico. (1–5) Holotype ALMNH:Paleo:21468, (1) lateral view; (2) close-up of cephalic appendages (mainly rostrum and scaphocerite); (3) close-up of tail fan; (4) close-up of pleonal somites and pleopods as preserved below it; (5) close-up of uropodal exopod with spinules (see arrow) on distal margin. a1 = antennula; a2 = antenna; pl1–pl5 = pleopods 1–5; r = rostrum; s1–s6 = pleonal somites 1–6; sc = scaphocerite; t = telson; uex = uropodal exopod.
Figure 2. Lobetelson feldmanni n. sp. from the Pennsylvanian (Kasimovian) Atrasado Formation (Tinajas Member, Unit 3B) of the Kinney Brick Quarry, New Mexico. (1–3) Holotype ALMNH:Paleo:21468, (1) pleon and tail fan, note ridge near upper margin of s6; (2) pleon, counterpart; (3) close-up of tail fan, counterpart, note spinules (see arrow) on distal end of upper exopod.
Figure 3. Lobetelson cf. L. feldmanni n. sp. from the Pennsylvanian (Kasimovian) Atrasado Formation (Tinajas Member, Unit 3A) of the Kinney Brick Quarry, New Mexico. (1–3) Specimen ALMNH:Paleo:21470, (1) lateral view; (2) close-up of cephalic appendages (mainly rostrum and scaphocerite), counterpart; (3) close-up of tail fan.
Figure 4. Drawings of the two specimens from the Pennsylvanian (Kasimovian) Atrasado Formation (Tinajas Member, Unit 3) of the Kinney Brick Quarry, New Mexico. (1) Holotype ALMNH:Paleo:21468 of Lobetelson feldmanni n. sp.; (2) Lobetelson cf. L. feldmanni n. sp., ALMNH:Paleo:21470.
Figure 5. Reconstructions of Belotelsonidea spp. in lateral views (1–5) and tail fan views (6–8). Reproduced with permissions: Factor and Feldmann (Reference Factor and Feldmann1985, fig. 12.1), Peach (Reference Peach1881, pl. 10.5f), Schram (Reference Schram1981b, fig. 2D, E), and Schram (Reference Schram2006, fig. 1).
Holotype
ALMNH:Paleo:21468
Diagnosis
Carapace elongate, subrectangular in lateral view, smooth; elongate sinuous pointed rostrum about as long as carapace, slightly downturned distally; rostrum with longitudinal lateral groove; elongate subrectangular s6 with thin longitudinal ridge parallel to dorsal margin; paddle-shaped uropodal exopod with longitudinal ridge at outer margin and curved groove paralleling inner margin; uropodal exopod distal margins with spinules.
Occurrence
Kinney Brick Quarry Lagerstätte, Manzanita Mountains, Tijeras, New Mexico, USA. Tinajas Member of the Atrasado Formation, Upper Pennsylvanian (Kasimovian). Location within quarry: 35.0009°, −106.3374 (WGS84). The type horizon is Unit 3B (Schneider et al., Reference Schneider, Legler, Brosig, Krainer and Lucas2021), which is a highly fossiliferous, finely laminated, fine-grained, blue/gray, limy shale. Several specimens of the bivalve Dunbarella occur on the same bedding plane as the holotype.
Description
Carapace
Elongate, smooth, subrectangular carapace completely enveloping cephalothorax with sinuous posterior margin and rounded orbits; rostrum flattened laterally, strongly elongate, sinuous, pointed, about as long as carapace, downturned distally, with distinct longitudinal continuous lateral thin groove paralleling dorsal margin, dorsal and ventral rostral margins unarmed.
Pleon
Subtriangular s1–s5; s3–s5 pleura slightly rounded ventrally; margins of s3–s5 pleura not rimmed; elongate subrectangular s6 with thin longitudinal ridge parallel to dorsal margin; convex ventral margin longer than s4–s5; long triangular telson narrowing distally, tip not preserved; dorsal surface of telson with proximally raised triangular smooth median bulge/keel, flanked by straight longitudinal grooves.
Cephalic appendages
Spherical eyes; a1 poorly preserved with fragments of three basal podomeres; a2 flagella partially preserved only; petaloid elongate scaphocerite extending forward with longitudinal marginal ridge; scaphocerite over one-half length of rostrum (as preserved).
Pleonal appendages
Partially preserved pl1–pl5, small and biramous; slender, elongate, and paddle-shaped uropods; uropodal exopod with a marginal ridge along outer margin and longitudinal curved groove along inner margin; uropodal exopod distal margins with spinules; uropodal endopods appear covered by telson.
Etymology
The species name honors the late Dr. Rodney Feldmann, a very prolific and respected fossil arthropod researcher active for over five decades and a much-appreciated mentor of more than 50 graduate students, including the first author.
Material
Holotype specimen (preserved in lateral view: part and counterpart), lacking thoracic appendages.
Measurements
Total length including rostrum (as preserved): ~92 mm; carapace length: ~23 mm; rostral length: ~23 mm; carapace height: ~15 mm.
Remarks
We assign this specimen to Belotelsonidea because of the well-developed carapace, the uropodal exopods are large, presence of biramous pleopods, and the telson is longer than wide and narrowing distally (consistent with the diagnoses in Schram, Reference Schram2006, and Schram and Koenemann, Reference Schram and Koenemann2021). Other stem malacostracans (see Schram and Koenemann, Reference Schram and Koenemann2021) differ in the proportion of the tail fan, rostrum, and/or carapace of the total length relative to belotelsonids. Schram (Reference Schram2006, p. 282) erected Lobetelson and designated L. mclaughlinae as the type species based on 25 specimens from the Middle Pennsylvanian Francis Creek Shale (Illinois, USA). The studied specimen shares the main morphological characters of Lobetelson, such as the very elongate rostrum nearly equal to the carapace length, the pleonal shape, elongated s6, and the lobate uropodal exopod. Species of Belotelson have a proportionally shorter rostrum, a proportionally shorter s6, and narrower uropods (Fig. 5, Table 2).
Based on a comparison between the studied specimen and the type species, we highlight some differences. The studied specimen has a sinuous rostrum with a lateral ridge, downturned distally (versus rostrum turned upward in Lobetelson mclaughlinae); s6 with a thin lateral dorsal ridge (versus smooth in L. mclaughlinae); uropodal exopod with a marginal ridge and an inner groove plus posterior fringed margin with spinules (versus single ridge and unarmed posterior margin in L. mclaughlinae). The holotype is larger than specimens of L. mclaughlinae. These combined differences justify the description of the new species Lobetelson feldmanni n. sp. to accommodate the studied specimen. The new species represents the youngest record for the genus, extending the stratigraphic range of Lobetelson from the Middle Pennsylvanian (Moscovian) to the Upper Pennsylvanian (Kasimovian).
Lobetelson feldmanni n. sp. differs from other malacostracans found in the same quarry. Uronectes kinniensis (order Anaspidacea) exhibits many more body segments and Aenigmacaris minima (order Aeshronectida) bears a much shorter rostrum and has a proportionally longer pleon.
Lobetelson cf. L. feldmanni new species
Occurrence
Kinney Brick Quarry Lagerstätte, Manzanita Mountains, Tijeras, New Mexico, USA. Location within quarry: 35.0010°, −106.3382 (WGS84). Tinajas Member of the Atrasado Formation, Upper Pennsylvanian (Kasimovian). The horizon is Unit 3A (Schneider et al., Reference Schneider, Legler, Brosig, Krainer and Lucas2021), a fossiliferous, finely laminated, fine-grained, brownish shale.
Material
ALMNH:Paleo:21470, specimen preserved in lateral view (part and part of counterpart).
Measurements
Total length including rostrum: ~117 mm; rostral length (as preserved): ~30 mm.
Remarks
Although the studied specimen is poorly preserved, it shows an elongate subrectangular carapace; elongate rostrum (broken anteriorly), flattened laterally with a thin groove best preserved at the tip, with dorsal and ventral rostral margins unarmed; s3–s5 pleura rounded ventrally; elongate, subrectangular s6, longer than the other somites; incomplete telson with a smooth median ridge; slender, elongate, paddle-shaped uropodal exopod, with a possible marginal ridge along the outer margin and a longitudinal curved groove near the inner margin.
Based on Schram (Reference Schram2006, p. 282), the studied specimen shares some of the main morphological characters of Lobetelson such as the very elongate rostrum nearly equal to carapace length, the pleonal shape, and the lobate uropodal exopod. Moreover, based on comparisons with the type species L. mclaughlinae and L. feldmanni n. sp., the studied specimen shows a relatively long subrectangular s6; a slender, elongate, paddle-shaped uropodal exopod with a marginal ridge and a possible, not well-preserved inner groove; and a rostrum with a lateral groove. These three characters are shared with L. feldmanni n. sp. In conclusion, based on these observations and considering the lack of a well-preserved pleon, and complete uropods useful for a specific assignment, we tentatively compare it to the new species.
Overview of Belotelsonidea
The four described species of Belotelsonidea thus far originate exclusively from the Carboniferous, spanning most of the period from the late Tournaisian to the Kasimovian or ca. 40 Myr (Fig. 6; Table 1). Paleobiogeographically, species are restricted to Scotland and various parts of the USA, near the equator to ~20° south (Fig. 7). The oldest records come from Scotland, but whether belotelsonids originated there and subsequently spread to the eastern part of the Panthalassic Ocean to what is now North America is difficult to evaluate based on the limited number of occurrences and species. New occurrences, although they will be uncommon due to the low preservation potential of swimming shrimp(-like) malacostracans relative to other crustaceans (Klompmaker et al., Reference Klompmaker, Portell and Frick2017), may shed more light on their paleobiogeography and migration patterns.
Figure 6. Stratigraphic ranges of Belotelsonidea spp. Numerical ages and color scheme derived from the International Stratigraphic Chart 09/2023 (updated from Cohen et al., Reference Cohen, Finney, Gibbard and Fan2013).
Figure 7. Paleobiogeographic occurrences of Belotelsonidea spp. plotted on a map representing the late Visean (Mississippian). Base map derived from Scotese (Reference Scotese2016).
Whereas most belotelsonids known thus far lived in near-shore marine environments, the oldest records from Scotland are interpreted to have also inhabited areas with limited to no marine influence (Briggs and Clarkson, Reference Briggs and Clarkson1989; Cater et al., Reference Cater, Briggs and Clarkson1989). Apparently, Belotelson from Scotland was able to tolerate different environmental conditions and salinity levels. In terms of diet, belotelsonids may have been scavengers but also may have consumed small prey near the bottom of the water column (Schram and Koenemann, Reference Schram and Koenemann2021). They may have been preyed upon by temnospondyls locally (Werneburg et al., Reference Werneburg, Schneider and Lucas2021) and probably by other animals higher in the food chain such as predatory fishes.
Acknowledgments
We thank Tom Suazo for discovering the holotype and the publishers for allowing reproduction of the drawings in Figure 5. Two reviewers and associate editor Carrie Schweitzer (Kent State University, Ohio, USA) are thanked for their insightful comments.
Competing interests
The authors declare none.
Data availability statement
Original and additional images of the holotype taken under normal and UV-A light and images from the other specimen taken under normal light are available via the Zenodo Repository: https://doi.org/10.5281/zenodo.10794847, https://doi.org/10.5281/zenodo.14630477
Open access
