Gerbil Classification

  • strict warning: Non-static method view::load() should not be called statically in /home/egerbilc/public_html/sites/all/modules/views/views.module on line 879.
  • strict warning: Declaration of views_handler_argument::init() should be compatible with views_handler::init(&$view, $options) in /home/egerbilc/public_html/sites/all/modules/views/handlers/views_handler_argument.inc on line 745.
  • strict warning: Declaration of views_handler_filter::options_validate() should be compatible with views_handler::options_validate($form, &$form_state) in /home/egerbilc/public_html/sites/all/modules/views/handlers/views_handler_filter.inc on line 589.
  • strict warning: Declaration of views_handler_filter::options_submit() should be compatible with views_handler::options_submit($form, &$form_state) in /home/egerbilc/public_html/sites/all/modules/views/handlers/views_handler_filter.inc on line 589.

Why do we use scientific names?

 If you notice that all gerbils, and in fact all species on earth are designated a two-part Latin name to identify them. This system of classifying animals is known as 'binomial nomenclature'. These names are important because they allow people around the world, no matter what language they speak, to write and communicate to others about any particular species. In theory, every name given is unique to that animal. The scientific names also give a clue as to what their relationships are to other animals. The name of each species is given a generic name and also a specific name. The generic name tells us what genus they come from. Some genera (plural) only have one species but the vast majority of them have many. So if we take the Mongolian gerbil, or Meriones unguiculatus, we quickly realise, that the generic part of its name, Meriones, has been applied to several other gerbils/Jirds, such as Shaw's jird (Meriones shawi,) Persian jird (Meriones persicus) Libyan jird (Meriones libycus) etc. These animals have all been given the same generic name because they all share very similar features and are much closer related to each other than any other species of rodents. The generic name is often the first level of taxonomic organisation, simply because all species that are thought to be closely related are placed together in a genus. If you notice in many examples, these Latin names can often be descriptive of the animal. It is also common for these scientific names to be named after people or often those that discover the animal, or even what region it is found in. An example of this is the Shaw's jird or Meriones shawi, or Meriones libycus the Libyan jird. However, In the case of the genus Meriones this wasn't the case and has led to some considerable confusion.  This can be seen with the Mongolian gerbil, or Meriones unguiculatus.  We have been taught in many books and on websites that the name roughly translates to "Clawed warrior". While it is true that Meriones was a Greek warrior with teeth on his helmet and was mentioned in Homers Iliad and that 'unguis' is Latin for nail, this wasn't the description that Johann Karl Wilhelm Illiger wanted to convey when he named the genus in 1811.  This confusion was further compounded In 1900 when Franz Eilhard Schulze introduced another genus group name, Idomeneus, based on the same-named companion of Meriones in the Trojan War.  If we take a closer look at Illeger's original description, it cleary shows this assumption as being incorrect.  Rather, Meriones derives from μηρος, the Greek word for the femur and Illiger accordingly calls the genus "Schenkelthier" in German, which roughly translates as "femur animal" as does Meriones.  For a more detailed explanation of this see here

Why the common names can be misleading

Common names by and large are not unique and can quite often lead to confusion over what animal is being referred to and what their relationships maybe to other animals. These scientific names help to prevent this. Good examples of common names leading to confusion are 'badgers'. If we take Honey badgers (Mellivora capensis), Eurasian badgers (Taxidea taxus), ferret badgers (Melogale personata) and stink badgers (Mydus javanensis). As we can see although they all share the common name of badger, but evolutionary wise, and scientifically speaking, they are not necessarily each other's closest relatives. Also we have to realise that common names rarely give us any insight into the animal's evolutionary history.

Taxonomy

This is the process of naming living organisms, and as such is constantly changing as we learn more about species, or even discover new species. Often when scientific understanding of an animal increases, it may also mean that the scientific name may be subject to change too. An example of this is the Mongolian gerbil, which until 1908 was known as Gerbillus unguiculatus. Often when the understandings of any animals increase they tend to be split into multiple genera, mainly in order to better represent important evolutionary differences amongst those species that are being studied.

Over the years many species have come to be known by several scientific names. In many cases one name is then chosen for the species and other names are known as 'synonyms' Again the Mongolian gerbil had several synonyms that in the past and were often referred to as subspecies, such as Meriones unguiculatus kurauchi, Meriones unguiculatus selenginus, Meriones unguiculatus kozlovi, and Meriones unguiculatus chihfengensis. All these are now regarded as Meriones unguiculatus, which is their currently recognised, valid name.

Over the years taxonomy has evolved a lot and scientists and researchers now agree that the best way of organizing the vast amount of living organisms and their biological diversity, is to organise them into groups that share a common or shared evolutionary history. One of the tools that have increased the revision of taxonomy recently has been the introduction of molecular data or DNA sequencing. As a result of this, a vast amount of species have now been reorganised, as previously a lot of the traditional ideas about related organisms, and which groups they belong to has been found to be quite inaccurate. At the present the classification of all the major groups of mammals are currently in flux, and as a continuing stream of new data emergences, phylogenetic hypotheses are constantly being updated. All the new data makes for very interesting reading and leads to valuable insights into the evolution of organisms and their associated traits, however it must be understood that at the same time that because of this it makes it very difficult to develop a stable classification system.

The Linnaean system

This was the old traditional system of biological classification of grouping species into 'ranks' such as genus, family, order, class, etc. but in many circumstances, this system of classifying animals is now regarded by scientists to be inaccurate and largely redundant. For e.g. within the old Linnaean ranking system there was actually a class for reptiles and also for birds, etc, but new scientific evidence that has been compiled has now found that birds actually share a common ancestry with crocodiles. This would mean that in the old style ranking system that birds would have to be either demoted to something below a 'class' level, or that this class should exist within another class, i.e. that of the reptiles. This in itself would confuse things further.

Today scientists and researchers try to make classification as 'rank free' as possible, and group hierarchies are based whenever possible on the current understanding of their evolutionary history.

Glossary of Terms

Classification

A system of naming species by their common characteristics. It is the systematic grouping of organisms based on structural or functional similarities due to a linked evolutionary history.

Taxonomy

Is the theory and practice of describing, naming, and the classification of living organisms into a system that indicates natural evolutionary relationships.

Phylogeny

Is the evolutionary history of a group or lineage.

Nomenclature

Is the system of scientific names applied to taxa (groups of organisms).

In the case here with the Mongolian gerbil, I have only used ranking labels at certain levels to indicate the traditional rank system, which was previously used for classification. These markers also help to indicate the current phylogenetic classification schemes with the older traditional system of classification. The Table in effect also represents our current understanding of the Mongolian gerbil's evolutionary history.

 


classification of the mongolian gerbil

  • * Eumetazoa/Metazoans- Animals whose bodies consist of many cells, as opposed to Protozoa, which are unicellular.
  •  *Deuterostomia/Deutorostomes- meaning "second mouth"- and are a superphylum of animals- and are opposed to the protostomes. Deuterostomes are distinguished by their embryonic development in deuterostomes, the first opening is the blastospore which becomes the anus, while in protostomes it becomes the mouth.
  • *Chordates- are a group of animals that includes the vertebrates, along with several closely related invertebrates. They have in common at some stage in their life, a notochord, which is a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a muscular tail extending past the anus.
  • *Tetrapods/Tetrapoda-tetrapod means 'four-legged' is a vertebrate animal having four feet and legs or leg like appendages. Amphibians, reptiles, dinosaurs and mammals are all classed as tetrapods, and even birds and snakes are tetrapods by descent, the term is mostly used in describing the earliest tetrapods, which radiated from the Sarcopterygii, or 'lobe-finned' fishes, into air-breathing amphibians in the Devonian period.
  • *Amniota/Amniotes-These are a group of vertebrates that have an amnion during embryonic development. They comprise of mammals, birds, and other groupings which are reptiles. Most are adapted to a fully terrestrial existence, although some are secondarily aquatic.
  • *Synapsida/Synapsids- Meaning 'fused arch', and are traditionally known as "mammal-like reptiles", and are a class of amniotes that developed a hole in their skull known as the temporal fenestra, behind the eyes, about 320 MYA during the late Carboniferous period. Today the 4,500 known species of living synapsids are known as mammals, and are currently the dominant land animals on earth.
  • *Therian Mammals-Theria means beasts, and is a subclass of advanced mammals that give birth to live young without using a shelled egg, including both placentals and marsupials. They are characterised by external ears, they suckle, and have an ankle specialized for power and range of motion. Therians are often classified by their specialized dentition. Almost all mammals are therians. The exceptions being the platypus and the echidnas (spiny anteater), both of which are known as monotremes.

Some notes on the order Rodentia

The old classification system within the order Rodentia used to include three suborders: Sciuromorpha (squirrel-like rodents), Myomorpha (rat-like rodents), and Hystricomorpha (porcupine-like rodents). These three terms are still used in many texts. However, the current classification system recognizes only two suborders, those are Sciurognathi and Hystricognathi. The older suborders Sciuromorpha and Myomorpha have been combined to become Sciurognathi. The Hystricomorpha fall entirely under Hystricognathi, with divisions here being between New and Old world groups.

Scuriothnagi now includes 11 families, Sciuridae (squirrels), Heteromyidae (Kangeroo rats, pocket mice & relatives, Geomyidae (pocket gophers), Muroidea (gerbils, mice & relatives), Dipodidae (Birch mice, jerboas, and jumping mice), Ctenodactylidae (Gundis), Castoridae (Beavers), Aplodontidae (Mountain beavers), Anomaluridae (Scaly-tailed squirrels), Pedetidae (Springhares) and Myoxidae (Dormice & Hazel mice

Currently the group Cricetidae, which previously included Cricetinae and Gerbillinae, as well as some other groupings, is now considered a separate family within Muroidea, like Muridae. Within the Crecitidae group are the subfamilies, Arvicolinae, or lemmings and voles etc, and Cricetinae, which are hamsters, also there are other families that are included, but these I mention are of interest to us because previously we grouped gerbils alongside these animals. Gerbils were previously grouped with these animals. Gerbillinae is currently classed separately because at the molecular level they have little in common with the family Cricetidae.

Sources

What is in a Scientific Name? - Tanya Dewey

Organismal classification - evolutionary relationships and ranks - Tanya Dewey Taxon tree- HCIL university of Maryland

 Article written by Eddie Cope

Back to the Gerbil Information Index