Hadrorhachia

Polypodia

Acanthopodia

**Hadrorhachia**

**Hadrorhachia** (lit. "stout spine") is a clade of Acanthopodia, common to pelagic environments and analogous to cartilaginous fish on Earth.

## Description

Hadrorhachia first emerged around 4060ma, when it diverged from the Orthorhachia branch.

The first Hadrorhachids used subcarangiform swimming, having a truncate caudal fin, and measured around 2 meters in length. While some species retain this form of locomotion, other species have evolved to use the other two forms of body-driven swimming. Native to pelagic environments, all observed Hadrorhachids employ some form of counter-shading.

Hadrorhachids dominated the pelagic ecosystem for over 150 million years, until the global climate shift resulted in the disruption of the oceanic ecosystem. While the Hadrorhachids survived, their top-level roles in the food chain were mostly overtaken by the Thalattotheres. However, the Hadrorhachids remain dominant in deeper waters due to their gill-based respiration.

### Branches

* Ptilopoda: Filter feeders, comprise the largest Acanthopods ever seen
* Teleopterida: Pelagic predators

## Navigation

* **Anthostoma**
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										+ *Eopteryx emmetti*
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													+ *Tachynectes jocomoli*†
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							+ *unspecified*
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								- *unspecified*
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							+ *unspecified*
								- *unspecified*
									* Onychognatha
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								- Isognatha
									* Myzognatha
										+ *Vitapatatoria aspiana*
									* Euisognatha
										+ Archeisognatha
										+ Cyanodermata

* **Polypodia**
	+ Tetrabrachia
		- Tachypodia
		- Acanthopodia
			* Orthorhachia
				+ Tanypterida
				+ Remipterida
					- Arheremipterida
					- Synopteridae
			* **Hadrorhachia**
				+ Ptilopoda†
					- *Bathytitan vendari*
				+ Euhadrorhachia
					- Diplocirridae
						* Archediplocirridae
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							+ *Kamakivenator cosmici*
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								- *unspecified*
									* Archeplatydontinae
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									* Xenodontia†
										+ Brachiocephalia†
										+ Euxenodontia†
											- Streptotarsi†
											- Archexenodontia†
								- Neoplatydontia
									* Pleuroptera
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											- Archepleuropteridae†
												* *Anthonomos qbelocki*†
											- Platyptera
												* *Sphenorhynchus sullivanae*
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											- *Carpophagus xeni*
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											- Euharpactopoda†
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												* *Cephalocarcinus elvari*†
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						* Edaphotheria
							+ Leptopoda
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										+ Euleptopodidae†
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										+ *Pycnothrix dicksoni*†
									* Allobrachidae†
										+ Euallobrachidae†
											- Corythobrachidae†
												* Archecorythobrachidae†
												* Camarabrachidae†
													+ *Cyanolophus mcgyveri*†
											- Archeallobrachidae†
												* Archeallobrachinae†
													+ *Melanothrix oneiropolos*†
												* Ceratobrachidae†
													+ *Thyreocephalus cryarchon*†
										+ Teleobrachidae†
											- *Therizinyx elliotti†*
							+ Eurycheridae
								- Archeurycheridae†
									* Archeurycheirinae†
										+ *Prolestes solysti*†
									* *Teratocheirus*†
										+ *Teratocheuirus philipi*†
								- Lystrocheiridae
									* Lystrocheirinae
										+ *Psammonyx deschaini*
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													+ Apodomorpha
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																	- Archecryptonychidae
																	- Neocryptonychidae
																		* Theristobrachidae
																		* Glyphonychidae
																			+ Archeglyphonychidae
																			+ Archonychidae
												* Acrocheiridae
													+ Euacrocheiridae
														- Archeacrocheiridae
														- Neoacrocheiridae
															* Heterognatha
																+ Distropheognatha
																	- Archedistropheognatha
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																		* Hadronychidae
																		* Daptodontia
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																		* Euprocaecoformidae
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															* Panhylotheria
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																	- Thaumatotheriidae
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																			+ Euhylotheriinae
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																	- Archethrinaxorhynchidae
																	- Dictyorhynchidae
													+ Apatocheiridae†
											- Oryctocheiridae
					- Dromaeopoda
						* Archedromaepoda†
							+ *Rhomaleopus*†
							+ Archedromaeopodidae†
								- *Dromovenator setnovi*†
						* Onychodontia
							+ Euonychodontia†
								- Euonychodontidae†
									* Ensidontia†
										+ Euensidontia†
										+ Prionodontia†
									* Euonychodontinae†
										+ Archeonychodontidae†
										+ Cryptodontia†
											- *Raptonyx junae*†
											- Tachydontia†
											- Eucryptodontia†
								- Hadrodontia†
							+ Allodontia
								- Euallodontia†
									* Archallodontia†
									* Eriotherinae†
								- Thecopoda
									* Euthecopoda†
										+ *Leucothrix caliburi*†
									* Amphidontia
										+ Archeamphidontia†
										+ Xenopsidae
											- *polylophodon thomasi*
											- Archexenopsidae
												* Archexenopsinae
												* Euxenopsidae
													+ Ankistrobrachidae
													+ Neoxenopsidae
														- Teleopsidae
														- Chelaphora
															* Stenochelaphora
															* Pachychelaphora
											- Stenopsidae
												* File:StenopsidaeEvo.pngArchestenopsidae
												* Neostenopsidae
													+ Peloropsidae
														- Archepeloropsidae
														- Anaxotheriidae
													+ Ceratodontia
														- Archeceratodontia
														- Neoceratodontia
															* Aratrodontia
															* Isodontia
																+ Kophodontidae
																+ Elaphrodontia
																	- Archelaphrodontia
																	- Neoelaphrodontia
																		* Spathodontia
																		* Xyrodontia
				+ Synischia
					- Megalobrachidae†
						* Archemegalobrachia†
							+ Archemegalobrachidae†
							+ Prenobrachidae†
						* Titanopoda†
							+ Procerapoda†
								- Euprocerapoda†
									* *Megaphagus matti*†
								- Stylopoda†
									* *Hybotitan bluenoti*†
							+ Baropoda†
								- Eubaropoda†
									* *Nanopus proximensis*†
									* Eubaropodidae†
								- Pachypoda†
					- Deinognatha
						* Eudeinognatha†
							+ Eudeinognathidae†
								- *Euoplos gulielmi*†
							+ Malleognatha†
						* Odontognatha
							+ Trachygnatha†
								- *Telmarchos krisi*†
							+ Dolichognatha
								- Eudolichognatha
									* Archedolichognatha†
									* Hybognatha
								- Pelagotheria†
									* Actatheria†
										+ *Eurypus geberi*†
									* Thalattotheria†
										+ Isopterygia†
										+ Anisopterygia†
											- *Pontodrakon nicholsi*†

* **Chemophyta**
	+ Archaeophyta
	+ Xenophyta
		- Caulophyta
			* Neocaulophyta
				+ Eucaulophyta
					- Eucaulophytaceae
						* Eucaulophytoideae
						* Nothodendrales†
					- Reptophyta
				+ Brachyphyta
					- Archebrachyphyta
						* Eubrachyphyta
							+ Eubrachyphytaceae
							+ Desmophyta
								- Carnophyta†
								- Chromatophyta
									* Archechromatophyta
										+ Archechromatophytacea
										+ Aphyllophyta
									* Zygophyta
										+ Zygophytacea
											- Zygodendrales
											- Archezygophytacea
										+ Harpactophyta†
						* Tylophyta
					- Cryptophyta
						* Eucryptophyta
						* Pagophyta
			* Necrophyta
		- Xylophyta
			* Euxylophyta
				+ Archexylophyta
					- Archexylophytacaea
					- Coelophyta
				+ Nodophyta
			* Altiphyta†
				+ *Trilobophyllus axidenti*†

 † = Extinct