# Marjum Formation

The Marjum Formation is a Cambrian geological formation that overlies the Wheeler Shale in the House Range, Utah. It is named after its type locality, Marjum Pass, and was defined in 1908. The formation is known for its occasional preservation of soft-bodied tissue, and is slightly younger than the Burgess Shale, falling in the Ptychagnostus praecurrens trilobite zone.

## Fossil content

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |

### Ambulacrarians

Ambulacrarians reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Castericystis | C. vali | | Numerous specimens. | A solutan. |
| Eldonia | E. ludwigi | Marjum Pass (Ptychagnostus punctuosus Zone). | SM X.50204.1 (part) & SM X.50204.2 (counterpart). | A cambroernid. |
| Marjumicystis | M. mettae | | 7 specimens. | An eocrinoid. |
| Mastigograptus | M. sp. | | A single specimen. | A mastigograptid graptolite. |
| Totiglobus | T.? lloydi | Locality 811. | 1 specimen (USNM 172047). | An edrioasteroid. |

### Arthropods

Arthropods reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Anomalocaris | A. nathorsti | Sponge Gully. | Partial body (USNM 374593). | Species moved to the genus Peytoia. |
| Asaphiscus | A. wheeleri | Bathyuriscus fimbriatus Subzone. | | A ptychopariid trilobite. |
| Baltagnostus | B. eurypyx | All subzones of the Bolaspidella Zone. | Multiple specimens. | A diplagnostid trilobite. |
| Bathyuriscidella | B. aff. B. amplicauda | Bolaspidella contracta Subzone. | 3 pygidia. | A dolichometopid trilobite. |
| Bathyuriscus | B. elegans | Bolaspidella contracta Subzone. | Numerous specimens. | A dolichometopid trilobite. |
| Bathyuriscus | B. fimbriatus | Bathyuriscus fimbriatus & lower Bolaspidella contracta Subzone. | Numerous specimens. | A dolichometopid trilobite. |
| Bolaspidella | B. contracta | Bolaspidella contracta & lower Lepojyge calva Subzones. | | A menomoniid trilobite. |
| Bolaspidella | B. housensis | Bathyuriscus fimbriatus Subzone. | | A menomoniid trilobite. |
| Bolaspidella | B. jarrardi | Localities 347, 391, and 716 (mid-Bolaspidella Zone). | Multiple specimens. | A menomoniid trilobite. |
| Branchiocaris | B. pretiosa | Sponge Gully. | 3 specimens. | A hymenocarine. |
| Buccaspinea | B. cooperi | Kells Knolls locality. | An almost complete specimen (BPM 1108). | A hurdiid, originally reported as Hurdia sp. |
| Burlingia | B. halgedahlae | Localities 347 and 716 (mid-Bolaspidella Zone). | Multiple specimens. | A burlingiid trilobite. |
| Caryosyntrips | C. camurus | 'Red Wash' locality. | 2 isolated frontal appendages. | A panarthropod of uncertain classification. |
| Cotalagnostus | C. laevus | Bolaspidella contracta Subzone. | Over 50 specimens. | A diplagnostid trilobite. |
| Cotalagnostus | C. sp. | Bolaspidella contracta Subzone. | A pygidium. | A diplagnostid trilobite. |
| Dicranocaris | D. guntherorum | Red Wash, Modocia Flats & Sponge Gully. | 4 specimens. | An arthropod of uncertain classification. |
| Dytikosicula | D. desmatae | West of Delta, House Range. | 1 specimen (SM X.50203). | A putative megacheiran. |
| Elrathia | E. alapyge | Bolaspidella contracta & Lejopyge calva Subzones. | Numerous specimens. | A ptychopariid trilobite. |
| Elrathia | E. marjumi | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | Numerous specimens. | A ptychopariid trilobite. |
| Emeraldella | E.? sp. | Red Wash. | Part & counterpart (KUMIP 204791). | An artiopod. |
| Hemirhodon | H. amplipyge | Bolaspidella contracta Subzone. | 14 incomplete specimens. | A dolichometopid trilobite. |
| Holteria | H. problematica | Marjum Pass (Lejopyge calva Subzone). | A pygidium. | A corynexochid trilobite. |
| Homagnostus | H. incertus | Bolaspidella contracta Subzone. | Multiple specimens. | An agnostid trilobite. |
| Hypagnostus | H. parvifrons | All subzones of the Bolaspidella Assemblage Zone. | Numerous specimens. | A diplagnostid trilobite. |
| Itagnostus | I. interstrictus | House Range. | | A peronopsid trilobite originally reported as Peronopsis interstricta. |
| Leanchoilia | L.? cf. protogonia | Sponge Gully. | Part & counterpart of a complete specimen (UU 06011.01). | A megacheiran. |
| Lejopyge | L. calva | Marjum Pass (Lejopyge calva Subzone). | Numerous specimens. | A ptychagnostid trilobite. |
| Linguagnostus | L. perplexus | Bolaspidella contracta Subzone. | Over 20 specimens. | A diplagnostid trilobite. |
| Marjumia | M. callas | Bolaspidella contracta Subzone. | | A marjumiid trilobite. |
| Marjumia | M. typa | Bolaspidella contracta Subzone. | | A marjumiid trilobite. |
| Modocia | M. laevinucha | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | Many specimens. | A marjumiid trilobite. |
| Modocia | M. nuchaspina | Bolaspidella contracta Subzone. | | A marjumiid trilobite. |
| Modocia | M. typicalis | | 50 or more specimens. | A marjumiid trilobite. |
| Naraoia | N. compacta | Sponge Gully. | 4 specimens. | A naraoiid. |
| Neolenus | N. inflatus | East of Antelope Springs. | Multiple specimens & fragments. | A trilobite. |
| Neolenus | N. intermedius | East of Antelope Springs. | | A trilobite. |
| Neolenus | N. intermedius pugio | East of Antelope Springs. | 4 specimens of a pygidium. | A trilobite. |
| Neolenus | N. superbus | East of Antelope Springs. | Multiple specimens & fragments. | A trilobite. |
| Nettapezoura | N. basilika | Sponge Gully. | | An arachnomorph. |
| Olenoides | O. decorus | Bolaspidella contracta Subzone. | 7 specimens. | A dorypygid trilobite. |
| Olenoides | O. inflatus | Bolaspidella contracta Subzone. | | A dorypygid trilobite. |
| Olenoides | O. marjumensis | Bolaspidella contracta Subzone. | | A dorypygid trilobite. |
| Olenoides | O. pugio | Bolaspidella contracta Subzone. | Numerous specimens. | A dorypygid trilobite. |
| Olenoides | O. superbus | Bolaspidella contracta Subzone. | 7 specimens. | A dorypygid trilobite. |
| Pahvantia | P. hastata | Precise localities unknown. | 3 specimens. | A hurdiid. |
| Peronopsis | P. interstricta | House Range. | Numerous specimens. | Reassigned to the genus Itagnostus. |
| Peronopsis | P. segmenta | House Range. | Multiple specimens. | A peronopsid trilobite. |
| Perspicaris | P.? ellipsopelta | Ptychagnostus punctuosus Zone. | Valves & carapaces. | A bivalved arthropod. |
| Peytoia | P. nathorsti | Sponge Gully. | Partial body (USNM 374593) & partial mouthpart (KUMIP 314095). | A hurdiid, formerly named Anomalocaris nathorsti. |
| Ptychagnostus | P. akanthodes | Bolaspidella contracta Subzone. | Numerous specimens. | A ptychagnostid trilobite. |
| Ptychagnostus | P. atavus | House Range. | | A ptychagnostid trilobite. |
| Ptychagnostus | P. hybridus | Bolaspidella contracta Subzone. | About 10 specimens. | A ptychagnostid trilobite. |
| Ptychagnostus | P. richmondensis | Bathyuriscus fimbriatus Subzone. | Numerous specimens. | A ptychagnostid trilobite. |
| Ptychagnostus | P. sp. | Bolaspidella contracta Subzone. | At least 5 pygidia. | A ptychagnostid trilobite. |
| Trymataspis | T. depressa | Bolaspidella contracta Subzone. | Over 30 specimens. | A lonchocephalid trilobite. |
| Trymataspis | T. lomaleie | Bolaspidella contracta Subzone. | 10 cranidia. | A lonchocephalid trilobite. |
| Trymataspis | T. pristina | Bolaspidella contracta Subzone. | Over 20 cranidia. | A lonchocephalid trilobite. |
| Tuzoia | T. guntheri | Ptychagnostus punctuosus Zone. | Multiple valves & carapaces. | A hymenocarine. |
| Utagnostus | U. trispinulus | Bolaspidella contracta & Lejopyge calva Subzones. | Multiple specimens. | An agnostid trilobite. |
| Utaspis | U. marjumensis | House Range & Wheeler Amphitheater. | | A ptychopariid trilobite. |
| Zacanthoides | Z. sp. | Wheeler Amphitheater (Bolaspidella contracta Subzone). | A cranidium. | A zacanthoidid trilobite. |

### Chancelloriids

Chancelloriids reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Chancelloria | C. sp. | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | About 20 spicules. | A chancelloriid. | |

### Chordates

Chordates reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Megasiphon | M. thylakos | House Range. | One specimen (UMNH.IP.6079). | A tunicate. |
| Nuucichthys | N. rhynchocephalus | House range. | One specimen (UMNH.IP.6084) | A basal chordate related to Metaspriggina. |
| Skeemella | S. clavula | North of Red Wash (Ptychagnostus punctuosus Biozone). | 2 specimens (KUMIP 314102 & KUMIP 314103). | A vetulicolian. |

### Cnidarians

Moon, Caron & Moysiuk (2023) considered these fossils would be ctenophores instead.
Cnidarians reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Coronatae? | Indeterminate | Sponge Gully. | 1 specimen (UU07021.05). | A scyphozoan jellyfish, may be referrable to the crown jellyfish family. |
| Cubozoa? | Indeterminate | Sponge Gully. | 2 specimens (UU07021.01 & UU07021.02). | Specimens possibly referrable to box jellyfish. |
| Narcomedusae? | Indeterminate | Sponge Gully. | 5 specimens (UU07021.03, UU07021.04, UU07021.06, UU07021.07 & UU07021.08). | A hydrozoan tentatively assigned to this family. |
| Semaeostomeae? | Indeterminate | Sponge Gully. | 2 specimens (UU07021.09 & UU07021.10). | A scyphozoan jellyfish tentatively assigned to this family. |

### Ctenophores

Ctenophores reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Ctenorhabdotus | C. campanelliformis | House Range (likely from the lower Ptychagnostus punctuosus Zone). | 1 specimen (UMNH.IP.6125). | A ctenophore. | |
| Thalassostaphylos | T. elegans | House Range (lower Ptychagnostus punctuosus Zone). | 1 specimen (UMNH.IP.6086). | A ctenophore. | |

### Lophotrochozoans

Lophotrochozoans reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Acrothele | A. subsidua | Bathyuriscus-Elrathina & Bolaspidella Zones. | | A brachiopod. |
| Helcionella | "H." arguta | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | More than 100 specimens. | A helcionellid. |
| Hyolithes | H. sp. | All subzones of the Bolaspidella Zone. | More than 100 specimens. | A hyolith. |
| Lingulella | L. sp. | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | | An obolid brachiopod. |
| Micromitra | M. modesta | | Multiple specimens. | A paterinide brachiopod. |
| Nisusia | N. sulcata | | 18 specimens. | A kutorginate brachiopod. |
| Pegmatreta | P. bellatula | Bathyuriscus fimbriatus & Bolaspidella contracta Subzones. | Numerous specimens. | A brachiopod. |
| Pegmatreta | P. ophirensis | All subzones of the Bolaspidella Zone. | | A brachiopod. |
| Pelagiella | P. sp. | Bolaspidella contracta Subzone. | More than 50 internal molds. | A pelagiellid. |
| Prototreta | P. attenuata | Bathyuriscus-Elrathina Zone & Bolaspidella Zone. | | A brachiopod. |
| Prototreta | P. mimica | Bolaspidella contracta Subzone. | | A brachiopod. |
| Stenothecoides | S. elongata | Bathyuriscus fimbriatus Subzone. | Over 30 valves. | A stenothecoid. |

### Scalidophorans

Scalidophorans reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Arrakiscolex | A. aasei | Grey Marjum locality (Ptychagnostus punctuosus Zone). | Cuticle fragments. | A palaeoscolecid also known from the Upper Weeks Formation. |
| Ottoia | O. prolifica | Sponge Gully. | A complete individual (KUMIP 204770). | Referral of the specimen to this species is insecure, better classified as O.? sp. |
| Ottoia | O.? sp. | Sponge Gully. | A complete individual (KUMIP 204770). | A stem-priapulid, specimen formerly referred to Ottoia prolifica or Scathascolex minor. |
| Scathascolex | S. minor | Sponge Gully. | A complete individual (KUMIP 204770). | Specimen reassigned to Ottoia? sp. |
| Selkirkia | S. willoughbyi | Sponge Gully. | Tube with associated soft parts (KUMIP 204788). | A stem-priapulid. |

### Sponges

Sponges reported from the Marjum Formation :
| Genus | Species | Presence | Material | Notes |
| Choia | C. carteri | Sponge Gulch. | | A demosponge. |
| Choia | C. hindei | Red Cliffs Wash. | 2 specimens & 3 other fragments. | A demosponge. |
| Choia | C. utahensis | Sponge Gulch. | Several specimens. | A demosponge. |
| Diagoniella | D. cyathiformis | Red Cliffs Wash & Kells Knolls Gulch. | Numerous specimens. | A reticulosan. |
| Diagoniella | D. hindei | Sponge Gulch. | Approximately 40 specimens. | A reticulosan. |
| Diagoniella | D. magna | Kells Knolls Gulch (Bathyuriscus fimbriatus zone). | A fragment (USNM 535922). | A reticulosan. |
| Diagoniella | D. sp. | Sponge Gulch. | 2 large fragments. | A reticulosan. |
| Hamptonia | H. bowerbanki | Red Cliffs Wash & Sponge Gulch. | Multiple specimens. | A demosponge. |
| Hazelia | H. palmata | Near Marjum Pass. | One specimen. | A demosponge. |
| Hintzespongia | H. bilamina | Kells Knolls Gulch (Bathyuriscus fimbriatus zone). | Multiple specimens. | A reticulosan. |
| Hexactinellida | Indeterminate | | Miscellaneous spicules. | Indeterminate glass sponges, originally reported as Hyalospongiae (now a junior synonym). |
| Kiwetinokia | | Drum Mountains. | 4 large slabs. | A reticulosan. |
| Leptomitus | L. metta | Red Cliffs Wash locality. | 22 specimens. | A demosponge. |
| Polygoniella | P. turrelli | House Range | Around 200 specimens | A glass sponge |
| Protospongia | P.? elongata | Sponge Gulch. | 1 specimen. | A reticulosan. |
| Testiispongia | T. venula | Sponge Gulch. | Several specimens. | A glass sponge. |
| Valospongia | V. gigantis | Sponge Gulch. | | A reticulosan. |
| Valospongia | V.? gigantus | Kells Knolls Gulch (Bathyuriscus fimbriatus zone). | A fragment (USNM 535917). | A reticulosan. |