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Dragonflies - living fossils

Evolution and Ancestors

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It is believed that the entire kingdom Animalia evolved from the same ancestor. This ancestor is believed to have been a colonial flagellated protist, found in the Precambrian era, more than 700 million years ago. One hypothesis proposes that the ancestral protist that evolved into the first animal developed an infolding of the cellular wall. This infolding created an inner pouch, which became the animal’s digestive system. (Campbell, Reece &, Mitchell, 1999, p.590) Animals rapidly diversified during the late Precambrian and early Cambrian (500 – 540 million years ago) periods. (Campbell et al., p.595)

Tachopteryx thoreyi belong to the phylum Arthropoda. Arthropoda have segmented bodies and an external skeleton. Also, most of them have compound as well as median eyes. Their body is open on the inside. They breathe through their body surface, gills, tracheae, or book lungs. Fertilization is internal for the majority. Most lay eggs, and many go through metamorphosis of some type. Fossils of ancestors of the phylum Arthropoda have been found in the Vendian period (540 – 600 million tears ago). During the Cambrian period (500 –540 million years ago), arthropods diversified rapidly. Paleodictyoptera, considered precursors of odonata ancestors, lived during the Upper Carboniferous period (280 - 360 million years ago). These large sturdy insects had wingspans of 20 to 50 cm across.

stenodictyapaleodictyopteragzelianepoch.gif

 wingspan 10 cm Stephanian Epoch (Upper Productive Coal Measures) - Gzelian epoch Commentry (Allier), France graphic from Rozvoj letenja - JTV page.

http://www.palaeos.com/Invertebrates/Arthropods/Insecta/Paleodictyoptera.html

Tachopetryx thoreyi belong to the class Insecta. Insecta bodies have three segments. They have three pair of legs that are attached to the middle segment (thorax). Usually they have two pair of wings. They have large compound eyes, usually three ocelli (median) eyes, and antennae. They have a digestive system, and breathe through tracheae or gills. Fertilization is internal for most. Also, the female have a storage area where they can store sperm and use this to fertilize multiple batches of eggs. Most insects are in a different form when they are young. They either go through complete metamorphosis, or hemimetabolous (partial metamorphosis). The class Insecta has more organisms that any other life form. Insect fossils have been discovered from the Devonian period, about 400 million years ago. (Campbell et al., 1999, p.618) During the Carboniferous and Permian (248 – 280 million years ago) periods, insects developed the ability to fly. Insects diversified rapidly after this. Insects are found in every type of environment on Earth. During the Carboniferous period, insects developed mouths specifically designed to feed on plants that grew at that time. (Campbell et al., p.619) The wings of insects developed from the outer skin of the insect, rather than from legs. This meant they still had limbs to grasp with, as well as to walk on. One of the first insects to evolve flight was the dragonfly (common name for order Odonata). The oldest fossils found of the order Odonata are those of Protodonata, which are 325 million years old (Pennsylvanian Period).

meganeura_monyiprotodonatalatepermianfree.gif

 Meganuera monyi Brongniart wingspan 75 cm Stephanian Epoch (Upper Productive Coal Measures) - Gzelian epoch Commentry (Allier), France family Meganeuridae - Bashkirian to  Kazanian (early Late Permian) graphic from Karl Von Zittel's Text-Book of Paleontology ed. Charles R. Eastman, 2nd ed. vol.1 1937 MacMillan & Co. London, p.809, fig.1567

http://www.palaeos.com/Invertebrates/Arthropods/Insecta/Protodonata.html

There is disagreement as to the relationship of the many suborders of living odonata. The debate revolves around the question as to whether Anisozygoptera and Anisoptera evolved from Zygoptera, or Zygoptera and Anisoptera evolved from Anisozygoptera. The general consensus is:

*   “Odonata is a monophyletic group which has been separated from Ephemeroptera, Neoptera, and the extinct Palaeodictyopteroidea since at least the lowermost Upper Carboniferous

*  The three extant suborders are closely related

*    Fossil suborder Archizygoptera is a subset of fossil suborder Protozygoptera

*    Modern Anisoptera is monophyletic.” (Trueman  & Rowe, 2001)

The following diagrams show the two current phylogeny theories. (Trueman  & Rowe, 2001).

 

 

Tillyard (1928) and Fraser (1957)

     ============================= Protodonata

     |

     |  ========================== Protanisoptera

=====|  |

     |  |  ======================= Protozygoptera

     ===|  |

        ===|          ============ Zygoptera (Coenagrionoidea)

           |          |

           =Zygoptera=|  ========= Zygoptera (Lestoidea, Calopterygoidea)

                      |  |

                      ===|  ====== Anisozygoptera (eg, Epiophlebia)

                         ===|

                            |  === Anisozygoptera (eg, Heterophlebia)

                            ===|

                               === Anisoptera

 

Handlirsch (1906-08)

     ================================== Protodonata

     |

     |  =============================== Protanisoptera

=====|  |

     |  |  ============================ Protozygoptera

     ===|  |

        ===|                  |======== Zygoptera

           |                  |

           ==Anisozygoptera===|  ====== Anisozygoptera (eg, Epiophlebia)

                              |  |

                              ===|  === Anisozygoptera (eg, Heterophlebia)

                                 ===|

                                    === Anisoptera

 

 

 

Identification of species is determined by the pattern of wing veins, distance between eyes, shape and position of tail appendages, and whether or not there is an ovipositor. The larvae are classified by appearance of its’ mouth, how it breathes, body spine pattern and shape of abdomen.

dragonflyanatomyillustration.gif

Anisoptera anatomy redrawn by me from multiple anatomy diagrams. The suborder Anisoptera has developed an enlarged rectal chamber with gills. They use this to take in extra oxygen, both on land and under water. It is believed they can also use the enlarged rectal chamber for “jet propulsion”. (Dunkle, 1981, p. 197) Tachopteryx thoreyi belong to the Petaluradae family. This family is characterized by eyes set wide apart, an ovipositor containing blades, and “long parallel-sided stigmas” on the wings. (Dunkle, p.31)The cerci of the male are large and flat, resembling a flower petal

petaluradae_family_larvae.gif

The Petaluradae family larvae have sturdy enough legs to walk on land.

They live in a partly wooded environment. These larvae resemble the flat shape of leaves and can cling closely. Prey must crawl around the larvae, and are more easily captured.  Because of this characteristic, is believed the petaluridae family has lived in deciduous forests for a long time. Adult Petaluradae also exhibit characteristics which suggest they have inhabited deciduous forests a long time. The flight season,when adults emerge, starts prior to the leaves coming out on the trees. This makes more sunny areas on the tree trunks, which the males typically perch on, while waiting for females. This behavior also helps to keep them warm during early spring weather. It is also believed that timing mating before trees are leafed out, makes it easier for females to find seeps, where they need to lay their eggs. (Seeps are where water trickles out of a hillside in a forest). (Dunkle, p.198)

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