# Lueders Formation

The Lueders Formation is a geologic formation in Texas. It is the top formation of the Albany Group and preserves fossils dating back to the Permian period.

## Description
### Paleogeography

At the time of deposition, a broad sea connected to the Panthalassic Ocean covered much of the central United States, including Texas. The Lueders Formation would have been located in the northern tropics or subtropics. Climatically, after the retreat of an early Artinskian glacial maximum, the deserts of the North American craton experienced fluctuation and growth during this time period, and the associated aridity decrease impacted seabed deposition in localities across the basin.

### Depositional environment

The Lueders Formation represents a deltaic environment, with terrestrial sediments being deposited onto the muddy bottom of a shallow estuary by shifting freshwater streams. In the Maybelle Member, the dolomite likely represents marine deposits, preserving marine sharks and fish, whereas darker terrestrial sediments and freshwater shale deposits contain remains of land animals and freshwater fish respectively.

## Fossil content
### Amphibians

Amphibians reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes |
| Crossotelos | C. annulatus | Maybelle Member. | Multiple specimens. | A nectridean. |
| Diplocaulus | D. magnicornis | Maybelle Member. | Multiple specimens. | A nectridean. |
| Eryops | E. megacephalus | Maybelle Member. | Limb & skull elements. | An eryopid. |
| Trimerorhachis | T. sp. | Maybelle Member. | Limb & skull elements. | A dvinosaur. |

### Fish
#### Acanthodians

Acanthodians reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Acanthodes | A. sp. | Maybelle Member. | A fin spine. | An acanthodiform, known from freshwater deposits. | |

#### Bony fish

Bony fish reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes |
| "Acrolepis" | | Maybelle Member. | Scales. | A palaeonisciform. |
| Gnathorhiza | G. serrata | Maybelle Member. | Jaw elements & near-complete specimen. | A lungfish from freshwater deposits. |
| Lawnia | L. cf. L. taylorensis | Maybelle Member. | Remains of millions of individuals. | A palaeonisciform originally reported as 'Lawnia-like', now thought to represent the genus itself. |
| Luederia | L. kempi | Maybelle Member. | A braincase & 2 large cleithra. | A marine palaeonisciform. |
| ?Platysomus | ?P. palmaris | Maybelle Member. | Partial bodies & numerous scales. | A marine (?) palaeonisciform. |
| Sagenodus | | Maybelle Member. | Upper tooth plate (UCLA VP 431). | A lungfish. |
| Schaefferichthys | S. leudersensis | Maybelle Member. | Incomplete specimen (USNM 23109). | A freshwater palaeonisciform. |
| ?Spermatodus | ?S. pustulosus | Maybelle Member. | Multiple specimens. | A coelacanth. |

#### Cartilaginous fish

Cartilaginous fish reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes |
| Acrodus | ?A. olsoni | | Teeth. | A hybodont. |
| Acrodus | ?A. sweetlacruzensis | | Teeth. | A hybodont. |
| Barbclabornia | B. luedersensis | | Numerous teeth. | A giant freshwater xenacanth. |
| Ctenacanthus | C. cf. C. amblyxiphias | Maybelle Member. | Fin spines. | A ctenacanth found in the marine dolomite. |
| Janassa | J. sp. | Maybelle Member. | Isolated teeth. | A petalodont found in the marine dolomite. |
| Orthacanthus | O. platypternus | | Teeth. | A freshwater xenacanth. |
| Orthacanthus | O. texensis | | Teeth. | A freshwater xenacanth. |
| Polyacrodus | P. wichitaensis | | Teeth. | A hybodont. |
| Polyacrodus | P. zideki | | Teeth. | A hybodont. |
| Xenacanthus | ?X. slaughteri | | Teeth. | A freshwater xenacanth. |
| Xenacanthus | X. sp. | Maybelle Member. | A tooth. | A freshwater xenacanth. |

### Synapsids

Synapsids reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Dimetrodon | D. sp. | Maybelle Member. | Neural spine & bone fragments. | A sphenacodontid. | |

### Invertebrates
#### Arthropods

Arthropods reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Ostracoda indet. | Indeterminate | | WSU 1445. | A fragmentary ostracod. | |
| Panduralimulus | P. babcocki | Maybelle Member. | Multiple specimens. | A horseshoe crab. | |

#### Bivalves

Bivalves reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Myalinella | M. sp. | | Valves (WSU 1407). | A myalinid. | |
| Pinnidae indet. | Indeterminate | | Shell. | An unknown pen shell. | |

#### Bryozoans

Bryozoans reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Bryozoa indet. | Indeterminate | | WSU 1430. | A fragmentary bryozoan. | |

#### Cephalopods

Cephalopods reported from the Lueders Formation :
| Genus | Species | Material | Notes |
| Koninckioceras | K. bibbi | Internal mold. | A nautiloid. |
| Metacoceras | M. sp. | Shell (WSU 1437). | A nautiloid. |
| Michelinoceras | M. sp. | Phragmocone (WSU 1406). | A orthocerid. |
| Millkoninckioceras | M. sp. | Shell (WSU 1442). | A nautiloid. |
| Perrinitidae indet. | Indeterminate | 3 specimens. | An ammonite. |
| Stenopoceras | cf. S. whitei | Phragmocone. | A nautiloid. |

#### Echinoderms

Echinoderms reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Crinoidea indet. | Indeterminate | | Columnal (WSU1405A). | A fragmentary crinoid. | |

### Plants

Plants reported from the Lueders Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Tinsleya | T. texana | Maybelle Member. | Numerous specimens. | A pteridosperm. | |
| Zeilleropteris | Z. wattii | | Leaves. | A gigantopterid. | |