Why Lord Shiva chose an elephant's head for Ganesha

Photo www.flickr.com/photos/arpana/sets/965242/
Today was Ganesha Chaturthi. In modern day terms, you could say, the birthday of one of the most belovedand well-known deities of the Hindu pantheon of Gods, without whose invocation and blessing no important work is ever begun, so much so that the Hindi idiom for inaugurating anything is “Sri Ganesha karna”!

We call him by many names, this Lord of All (Vinayaka), each one both a paen and a prayer. Lambhodara or he of a belly large enough to accommodate the entire universe, the Giver of Boons (Varadavinayaka) and Knowledge (Vidyavaridhi), the Destroyer of Obstacles (Vighnavinashanaya, Vigneshwara). We have grown up listening to and reading the wonderful stories about him. The devoted son (Eshanputra, Rudrapriya Shambhavi, Gaurisuta), who not just lost a tusk defending his father from the wrath of the mighty Parasurama and thus became known as Ekdanta, but who also defined the meaning of filial love for all time to come by circling his parents when asked by them to circle the universe. The divine chronicler who, not happy to just be Vyasa’s stenographer, stipulated that he would do the job only if the sage recited the Mahabharata in one uninterrupted stretch and who in turn fulfilled Vyasa’s counter condition that in that uninterrupted flow, he would not write down anything that he did not understand. (It was in these conditions that the Mahabharata was completed in 3 years!)
And so naturally, this infinite repository of wisdom (Buddhinath, Buddhipriya, Buddhividhata) became the consort of not just Buddhi but also Siddhi, worshipped ever since as not just Vinayaka but Siddhivinayaka. But perhaps the most popular story is the one of how our Lord Ganesha got his elephant head (Gajanana, Gajakarna, Gajananeti). There are many versions and I must confess that my own favourite is the one about him standing guard for his mother Parvati. But as I searched for and read all the versions, I couldn’t help wondering. Why an elephant head and why not that of some other animal?

I know that there will be many answers to this, most of them from reli