Very interesting question. I found a site that seems to have a lot of information concerning which fruits are tangerine vs. tangelos, where they’re grown, history of etc. Hope it helps. I’ll also be perusing the page to find out a little more info myself to find out more about my favorite the satsuma’s.
Mandarin: a small, spiny citrus tree, Citrus reticulata, native to China, bearing lance-shaped leaves and flattish, orange-yellow to deep-orange loose-skinned fruit, some varieties of which are called tangerines.
Satsuma: 1. a former province on S Kyushu, in SW Japan: famous for its porcelain ware.
2. (lowercase) a kind of mandarin orange.
Clementine: a small, sweet variety of tangerine with orange-red skin.
Tangerine: Also called mandarin, mandarin orange. any of several varieties of mandarin, cultivated widely, esp. in the U.S.
So in answer to your question, they’re all just spin-offs of the mandarin, so you probably wouldn’t be able to tell the difference. I looked it up on images.google.com, and I can’t see the difference. I also found out that mandarin is also the name of a very pretty bird…go figure.
Description & storage
Orange: Round thick skinned juicy edible fruit that is a reddish-yellow color when ripe.
Mandarin types: type of small orange with loose skin.
Store them at 12 degrees Celcius (=57o F) or if you like in the refrigerator. This is nice when you use them for squeezing.
Clementines: the clementine is a seedless mandarin.
Kumquats: the kumquat is like a citrus fruit and has an edible skin. It is the most well known of the sort fortunella which is closely related to Citrus.
Mandarins: type of small orange with loose skin. The mandarin got its name because it was exploited by high-ranking government officials in China (mandarins).
Minneolas: are a crossing between a tangerine and a grapefruit and can be recognized by
"the little nose". Can be peeled manually. Is a type of
Tangelo, a minneola is a specifically marketed tangelo.
Oranges: There are different types of oranges: navel oranges, Valencia oranges and blood oranges are the most cultivated races.
Tangelos: a tangelo is a crossing between a tangerine, a grapefruit and an orange. A specific kind of tangelo is the
Ugli which is described further on this page.
Satsuma:is a very special seedling from Japan. Its skin is a bit tighter than the clementine and it doesn’t have seeds as well.
Tangerines: a tangerine is an orange-red mandarin with a particular citrus taste. Can be peeled manually.
Uglis: a specific kind of tangelo, easier to peel. A crossing between a tangerine, a grapefruit and an orange. Looks really ugli and sometimes has brown spots. Can be peeled manually.
Very interesting question. I found a site that seems to have a lot of information concerning which fruits are tangerine vs. tangelos, where they’re grown, history of etc. Hope it helps. I’ll also be perusing the page to find out a little more info myself to find out more about my favorite the satsuma’s.
http://www.tonytantillo.com/fruits/tangerines.html
Mandarin: a small, spiny citrus tree, Citrus reticulata, native to China, bearing lance-shaped leaves and flattish, orange-yellow to deep-orange loose-skinned fruit, some varieties of which are called tangerines.
Satsuma: 1. a former province on S Kyushu, in SW Japan: famous for its porcelain ware.
2. (lowercase) a kind of mandarin orange.
Clementine: a small, sweet variety of tangerine with orange-red skin.
Tangerine: Also called mandarin, mandarin orange. any of several varieties of mandarin, cultivated widely, esp. in the U.S.
So in answer to your question, they’re all just spin-offs of the mandarin, so you probably wouldn’t be able to tell the difference.
I looked it up on images.google.com, and I can’t see the difference. I also found out that mandarin is also the name of a very pretty bird…go figure. 
Differences:
Sweet Orange
Citrus sinenis
Family: Rutaceae
Clementine, Mandarin, Tangerine, Satsuma
Citrus reticulata,
Family: Rutaceae
Description & storage
Orange: Round thick skinned juicy edible fruit that is a reddish-yellow color when ripe.
Mandarin types: type of small orange with loose skin.
Store them at 12 degrees Celcius (=57o F) or if you like in the refrigerator. This is nice when you use them for squeezing.
Clementines: the clementine is a seedless mandarin.
Kumquats: the kumquat is like a citrus fruit and has an edible skin. It is the most well known of the sort fortunella which is closely related to Citrus.
Mandarins: type of small orange with loose skin. The mandarin got its name because it was exploited by high-ranking government officials in China (mandarins).
Minneolas: are a crossing between a tangerine and a grapefruit and can be recognized by
"the little nose". Can be peeled manually. Is a type of
Tangelo, a minneola is a specifically marketed tangelo.
Oranges: There are different types of oranges: navel oranges, Valencia oranges and blood oranges are the most cultivated races.
Tangelos: a tangelo is a crossing between a tangerine, a grapefruit and an orange. A specific kind of tangelo is the
Ugli which is described further on this page.
Satsuma:is a very special seedling from Japan. Its skin is a bit tighter than the clementine and it doesn’t have seeds as well.
Tangerines: a tangerine is an orange-red mandarin with a particular citrus taste. Can be peeled manually.
Uglis: a specific kind of tangelo, easier to peel. A crossing between a tangerine, a grapefruit and an orange. Looks really ugli and sometimes has brown spots. Can be peeled manually.
hope this helped.