Satan eurystomus

Hubbs and Bailey 1947

Satan eurystomus
Redrawn by Rhian Kendall from Hubbs and Bailey (1947)






Only a holotype has been assigned: UMMZ 190922 (ex WMM 31.P.16.5) immature male 68.7mm SL. This species is the type species by original designation and monotypy of the cave‑restricted genus Satan.


This species (and its confamilial Trogloglanis pattersoni) is restricted to very deep artesian waters (up to 600m) in the Central, or San Antonio, Pool of the Edwards Aquifer, Bexar County, Texas, USA (29o30’N, 98o30’W). It is distributed over an area of at least 500 km2 but has only been collected from man‑made wells which penetrate the aquifer. The collection localities are given below with depth in metres.

Artesian wells from which Satan eurystomus has been collected. Compiled from data in Longley and Karnei (1979). There may be more recent records from other sites.


O.R. Mitchell Well 528
William Kempin Well 381
El Patio Foods Well 430
Bexar Metropolitan Water District Well ?
Artesia Well 402
Josef Boecke Well   308
Alamo Dressed Beef Company Well    ?
Persyn Well ?



The underground cavities inhabited by this species and Trogloglanis pattersoni are probably the most extreme of any  from which cave dwelling fishes are known. Details of the actual habitat are of course unknown and will probably remain so. What little is known has been gleaned from samples taken at the wells. Longley (1981) considered the aquifer to be the earths most diverse groundwater ecosystem and summarised its fauna. Kuehn and Koehn (1991) and Kuehn, O’Neil and Koehn (1992) isolated various fungi and algae which may play an important role in the trophic economy of the system.  Northup and Lavoie (2001) suggest that bacteria growing at the interface between saline and freshwater may take part in the food web within this aquifer.  Moraver and Huffman (1988) report the parasitic nematode Rhabdochona longleyi from both species of fishes. The most detailed account of the animals and their environs is that of Longley and Karnei (1979,1979).


There are currently two principle hypotheses for the relationships of Satan eurystomus which are summarized in detail by Arce et al. (2016) and Lundberg et al. (2017). First is the relationship with the epigean and monotypic Pylodictis olivaris (Rafinesque 1818), first suggested by Taylor (1969) in his revision of Noturus. Lundberg et al. (2017) used HRXCT imaging to study the skelton of Satan and found 10 synapomorphies between the two species (see Dahdul et al. 2010 for details of the terminology) : 1. Head shape and mouth position, 2. Mesethmoid bone shape, 3. Lateral ethmoid posterior process, 4. Supraoccipital posterior process, 5. Parasagittal and occipital crests, 6. Opercular frame and panel, 7. First mandibular sensory canal pore, 8. Preoperculo-mandibular sensory canal foramina and pores, 9. Posterior ceratohyal, 10. Fourth supraneural and anterior nuchal plate. Some of these anatomical features are related to suction feeding in Pylodictis and Satan. There are a number of uncertainties in other anatomical features. The second hypothesis is that the four North and Central American troglobitic ictalurids Satan eurystomus, Trogloglanis pattersoni, Prietella phreatophila and P. lundbergi  form a monophyletic group with fifteen synapomorphies (Arce et al. 2016): 1. Absence of eyes, 2. depigmentation, 3. Fifth vertebra, 4. Lateral line extent, 5. Mesethmoid cornua, 6. Anterior cranial fontanel, 7. Descending wing of frontal, 8. Supraoccipital posterior process, 9. Pterotic wings, 10. Parasphenoid and orbitosphenoid, 11. Abductor arcus palatine scars, 12. Anterior ceratohyal-ventral hypohyal joint, 13. Dorsal hypohyal, 14. Upper hypurals, 15. Transcapular ligament ossification. In addition to these synapomorphies Satan exhibits a number of singular features not seen in the other three ictalurid troglobites (Lundberg et al. 2017:155-157). It would be highly valuable to compare these anatomical synapomorphies with those from molecular markers but there are no suitable specimens of Satan from which to obtain tissue samples and no new living specimens have been seen for a decade or more.

See also the entry for Trogloglanis pattersoni.


Conservation Status

[VU D2:3.1:2014]

(NatureServe. 2014. Satan eurystomus. The IUCN Red List of Threatened Species 2014: Downloaded on 07 July 2017). V (Miller, 1977), R (IUCN, 1988), V (IUCN, 1990), V (IUCN, 1993), VU D2 (IUCN, 1996, 2000). T1 (Williams, Johnson, Hendrickson, Contreras-Balderas, Williams., Navarro-Mendoza, McAllister and Deacon, 1989). G1 (NatureServe, 2002). This species is potentially threatened by overpumping of the aquifer, which is the primary source of water for people in the region. In the 1990s the world's largest water well (at that time) was drilled close to the known habitat of the species, and the water was briefly used to support a catfish farm; subsequently the well and water rights were purchased by the San Antonio Water System, which now uses the well for aquifer monitoring purposes. Depletion of the aquifer poses a threat by possibly allowing the poor-quality anaerobic water of the "bad water" zone to replace good-quality water where the fish now resides (G. Longley, The Handbook of Texas Online).

Pollution from industrial and agricultural sources is a potential threat, but protection of the aquifer for human uses will probably also protect the fish.

Longley and Karnei (1979b) point out, however, that the greatest threat to this animal is from depletion of the groundwater by pumping. Groundwater pollution could also pose a serious threat, especially in the light of the evidence gathered by Winograd and Robertson (1982) that the residence time of water in very deep aquifers may be as much as 10000 years. See also the San Marcos Recovery Plan (Edwards, Beaty, Longley, Riskind, Tupa and Whiteside 1984).

Museum Holdings

The only known Museum specimens of this species are (Lundberg, Hendrickson, Luckenbill and Arce 2017)

NLU 47110 (60.9mm SL)

NLU uncataloged (formerly LTU 11342) (74.1mm SL)

TCWC 8279.01 (108mm SL)

TCWC 8280.01 (63mm SL)

TCWC 8281.01 (112mm SL)

TNHC 18764 (70mm SL)

TNHC 21702 (96mm SL)

TNHC 25142 (87.9mm SL)

TNHC 63279 (69mm SL) (previously at STSU)

TU 10809 (77.3mm SL) (Suttkus 1961)

TX State University San Marcos uncataloged teaching collection (102mm SL)

UMMZ 190922 (68.7mm SL) (holotype)

USNM 195830 (88.7mm SL) (Suttkus 1961)

USNM 205383 (73mm SL)

Longley and Karnei (1979), and Langecker and Longley (1993) reported that there were up to 21 specimens (30–114 mm SL) at STSU but some may have ben lost as  Lundberg et al. (2017) could find only two (TNHC 63279 and TX uncatalogued). One other specimen WMM 25.193.37.G is also now lost.

Key References

Hubbs, C. L. and Bailey, R. M. Journal Article 1947 Blind catfishes from artesian waters of Texas
Taylor, W. R. Thesis 1955 A revision of the genus Noturus Rafinesque with a contribution to the classification of the North American catfishes
Suttkus, R. D. Journal Article 1961 Additional information about blind catfishes from Texas
Taylor, W. R. Journal Article 1969 A revision of the catfish genus Noturus Rafinesque, with an analysis of higher groups in the Ictaluridae
Reddell, J. R. and Mitchell, R. W. Journal Article 1969 A checklist and annotated bibliography of the subterranean aquatic fauna of Texas
Lundelius, E. L. and Slaughter, B. H. Book 1971 Natural history of Texas caves
Hubbs, C. Book Section 1971 Fishes of Texas caves
Species, Texas Organisation for Endangered Journal Article 1975 T.O.E.S. watchlist of endangered, threatened and peripheral vertebrates of Texas
Longley, G. and Karnei, H. Journal Article 1979 Status of Trogloglanis pattersoni Eigenmann, the toothless blindcat
Longley, G. and Karnei, H. Journal Article 1979 Status of Satan eurystomus Hubbs and Bailey, the widemouth blindcat
Longley, G. Journal Article 1981 The Edwards aquifer: Earths most diverse groundwater ecosystem ?
Lundberg, J. G. Journal Article 1982 The comparative anatomy of the toothless blindcat, Trogloglanis pattersoni Eigenmann, with a phylogenetic analysis of the ictalurid fishes
Winograd, I. J. and Roberston, F. N. Journal Article 1982 Deep oxygenated groundwater: anomaly or common occurence ?
Edwards, R. J., Beaty, H. E., Longley, G., Riskind, D. H., Tupa, D. D. and Whiteside, B. G. Book 1984 The San Marcos recovery plan
Woodruff, C. M. and Abbott, P. L. Book Section 1986 Stream piracy and the evolution of the Edwards Aquifer along the Balcones escarpment, central Texas
Longley, G. Book Section 1986 The biota of the Edwards Aquifer and the implications for zoogeography
Species, Texas Organisation for Endangered Journal Article 1988 Endangeredthreatened and watchlist of vertebrates of Texas
Moraver, F. and Huffman, D. G. Journal Article 1988 Rhabdochona longleyi sp. n. (Nematoda, Rhabdochonidae) from the blind catfishes, Trogloglanis pattersoni and Satan eurystomus (Ictaluridae) from the subterranean waters of Texas
Kroschewsky, J. R. Journal Article 1990 The Edwards Aquifer Research and Data Centre: Objectives and accomplishments
Kuehn, K. A. and Koehn, R. D. Journal Article 1991 Fungal populations isolated from Ezells Cave in south Texas
Langecker, T. G. and Longley, G. Book Section 1992 Blind catfish (Trogloglanis pattersoni and Satan eurystomus) from dep artesian waters. A study on convergent adaptations to cave and deep sea biota
Langecker, T. G. and Longley, G. Journal Article 1992 Blind catfish (Trogloglanis pattersoni and Satan eurystomas) from deep artesian waters: A study on convergant adaptation to cave and deep sea biotas
Kuehn, K. A., O'Neil, R. M. and Koehn, R. D. Journal Article 1992 Viable photosynthetic microalgal isolates from aphotic environments of the Edwards Aquifer (central Texas)
Lundberg, J. G. Book Section 1992 The phylogeny of ictalurid catfishes: a synthesis of recent work
Langecker, T. G. and Longley, G. Journal Article 1993 Morphological adaptations of the Texas blind catfishes Trogloglanis pattersoni and Satan eurystomus (iluriformes, Ictaluridae) to their underground environment
Bowles, D.E. and Arsuffi, T.L. Journal Article 1993 Karst aquatic ecosystems of the Edwards Plateau region of central Texas, USA: A consideration of their importance, threats to their existence, and efforts for their conservation
Krejca, J, Hendrickson, DA and Taylor, SJ Journal Article 2000 Using stygobites to follow groundwater in Texas and Mexico
Northup, D.E. and Lavoie, K.H. Journal Article 2001 Geomicrobiology of caves: A review
Wilcox, TP, Garcia de Leon, FJ, Hendrickson, DA and Hillis, DM Journal Article 2004 Convergence among cave catfishes: long-branch attraction and a Bayesian relative rates test
Boghici, R. Report 2004 Hydrogeology of Edwards–Trinity Aquifer of Texas and Coahuila in the Border Region
Sullivan, JP, Lundberg, J. G. and Hardman, M Journal Article 2006 A phylogenetic analysis of the major groups of catfishes (Teleostei: Siluriformes) using rag1 and rag2 nuclear gene sequences
Dahdul, WM, Lundberg, J. G., Midford, PE, Balhoff, JP, Lapp, H, Vision, TJ, Haendel, MA, Westerfield, M and Mabee, PM Journal Article 2010 The Teleost anatomy ontology: Anatomocal representation for the genomics age
Egge, JJD Book Section 2010 Systematics if ictalurid catfishes: a review of the evidence
Zara Environmental LLC Report 2010 Final Report for deep aquifer study of the Edwards Aquifer
Zara Environmental LLC Report 2014 Fauna of wells near the saline waterline of the Edwards Aquifer, Texas
Arce, M, Lundberg, J. G. and O'Leary, MA Journal Article 2016 Phylogeny of the North American catfish Family Ictaluridae (Teleostei: Siluriformes) combining morphology, genes and fossils
Airhart, M.G. Web Page 2017 Scientists on the trail of central Texas' elusive Satan fish
Lundberg, J.G., Hendrickson, D.A., Luckenbill, K.R. and Arce M Journal Article 2017 Satan's skeleton revealed: a tomographic and comparative osteology of Satan eurystomus, the subterranean Widemouth Blindcat (Siluriformes, Ictaluridae)

Internet Resourses

A note on recent revived interest in this species

Images and further information for the paper by Lundberg, Hendrickson, Luckenbill and Arce (2017) are at the following links:

Tomographic image stacks of TCWC 8279.01

Tomographic image stacks and a selection of 3-D animations of USNM 195830

Tomographic image stacks and a selection of 3-D animations of both USNM 195830 and TCWC 8279.01

The Hanbook of Texas Online has an account of this species:

and also one on Trogloglanis pattersoni:

Dean Hendrickson's lab. web page contains the most up to date information on Satan and Trogloglanis:

Zara Environmental LLC have done extensive fieldwork in the Edwards Aquifer